161

161 is the sum of five consecutive prime numbers: 23, 29, 31, 37, and 41
161 is a hexagonal pyramidal number.
161 is a semiprime. Since its prime factors 7 and 23 are both Gaussian primes, 161 is a Blum integer.
161 is a palindromic number
⁠161/72⁠ is a commonly used rational approximation of the square root of 5 and is the closest fraction with denominator <300 to that number.