diff --git a/kernel/log.cc b/kernel/log.cc
index 34e56f8ac..55caea250 100644
--- a/kernel/log.cc
+++ b/kernel/log.cc
@@ -90,11 +90,11 @@ int gettimeofday(struct timeval *tv, struct timezone *tz)
 	QueryPerformanceFrequency(&freq);
 	QueryPerformanceCounter(&counter);
 
-	counter.QuadPart *= 1000000;
+	counter.QuadPart *= 1'000'000;
 	counter.QuadPart /= freq.QuadPart;
 
 	tv->tv_sec = long(counter.QuadPart / 1000000);
-	tv->tv_usec = counter.QuadPart % 1000000;
+	tv->tv_usec = counter.QuadPart % 1'000'000;
 
 	return 0;
 }
@@ -135,7 +135,7 @@ static void logv_string(std::string_view format, std::string str) {
 				initial_tv = tv;
 			if (tv.tv_usec < initial_tv.tv_usec) {
 				tv.tv_sec--;
-				tv.tv_usec += 1000000;
+				tv.tv_usec += 1'000'000;
 			}
 			tv.tv_sec -= initial_tv.tv_sec;
 			tv.tv_usec -= initial_tv.tv_usec;
diff --git a/passes/cmds/select.cc b/passes/cmds/select.cc
index 6da15c19a..0df47664f 100644
--- a/passes/cmds/select.cc
+++ b/passes/cmds/select.cc
@@ -570,7 +570,7 @@ static void select_op_expand(RTLIL::Design *design, const std::string &arg, char
 		ct.setup(design);
 
 	if (pos < int(arg.size()) && arg[pos] == '*') {
-		levels = 1000000;
+		levels = 1'000'000;
 		pos++;
 	} else
 	if (pos < int(arg.size()) && '0' <= arg[pos] && arg[pos] <= '9') {
diff --git a/passes/opt/opt_muxtree.cc b/passes/opt/opt_muxtree.cc
index 2f7d26dcf..0020af09f 100644
--- a/passes/opt/opt_muxtree.cc
+++ b/passes/opt/opt_muxtree.cc
@@ -64,7 +64,7 @@ struct OptMuxtreeWorker
 	RTLIL::Module *module;
 	SigMap assign_map;
 	int removed_count;
-	int glob_evals_left = 10000000;
+	int glob_evals_left = 10'000'000;
 
 	struct bitinfo_t {
 		// Is bit directly used by non-mux cells or ports?
diff --git a/passes/techmap/extract_fa.cc b/passes/techmap/extract_fa.cc
index 1984f82f5..46ab7e520 100644
--- a/passes/techmap/extract_fa.cc
+++ b/passes/techmap/extract_fa.cc
@@ -40,10 +40,10 @@ int bindec(unsigned char v)
 	r += (~((v & 2) - 1)) & 10;
 	r += (~((v & 4) - 1)) & 100;
 	r += (~((v & 8) - 1)) & 1000;
-	r += (~((v & 16) - 1)) & 10000;
-	r += (~((v & 32) - 1)) & 100000;
-	r += (~((v & 64) - 1)) & 1000000;
-	r += (~((v & 128) - 1)) & 10000000;
+	r += (~((v & 16) - 1)) & 10'000;
+	r += (~((v & 32) - 1)) & 100'000;
+	r += (~((v & 64) - 1)) & 1'000'000;
+	r += (~((v & 128) - 1)) & 10'000'000;
 	return r;
 }
 
diff --git a/tests/cxxrtl/test_value_fuzz.cc b/tests/cxxrtl/test_value_fuzz.cc
index a77120136..e5518ae8a 100644
--- a/tests/cxxrtl/test_value_fuzz.cc
+++ b/tests/cxxrtl/test_value_fuzz.cc
@@ -39,7 +39,7 @@ struct BinaryOperationBase
 template<size_t Bits, typename Operation>
 void test_binary_operation_for_bitsize(Operation &op)
 {
-	constexpr int iteration_count = 10000000;
+	constexpr int iteration_count = 10'000'000;
 
 	constexpr uint64_t mask = std::numeric_limits<uint64_t>::max() >> (64 - Bits);