155531 has 4 divisors (see below), whose sum is σ = 159192. Its totient is φ = 151872.

The previous prime is 155521. The next prime is 155537. The reversal of 155531 is 135551.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 135551 = 13 ⋅10427.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-155531 is a prime.

It is a super-2 number, since 2×155531² = 48379783922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (155537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1766 + ... + 1851.

It is an arithmetic number, because the mean of its divisors is an integer number (39798).

2¹⁵⁵⁵³¹ is an apocalyptic number.

155531 is a deficient number, since it is larger than the sum of its proper divisors (3661).

155531 is an equidigital number, since it uses as much as digits as its factorization.

155531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3660.

The product of its digits is 375, while the sum is 20.

The square root of 155531 is about 394.3741877963. The cubic root of 155531 is about 53.7781248159.

Adding to 155531 its sum of digits (20), we get a palindrome (155551).

It can be divided in two parts, 1555 and 31, that multiplied together give a triangular number (48205 = T₃₁₀).

The spelling of 155531 in words is "one hundred fifty-five thousand, five hundred thirty-one".