155961 has 24 divisors (see below), whose sum is σ = 256256. Its totient is φ = 90720.

The previous prime is 155921. The next prime is 156007. The reversal of 155961 is 169551.

155961 is a nontrivial binomial coefficient, being equal to C(559, 2).

It is not a de Polignac number, because 155961 - 2⁷ = 155833 is a prime.

It is an Ulam number.

Its product of digits (1350) is a multiple of the sum of its prime divisors (90).

It is not an unprimeable number, because it can be changed into a prime (155921) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3606 + ... + 3648.

2¹⁵⁵⁹⁶¹ is an apocalyptic number.

155961 is the 558-th triangular number.

It is an amenable number.

155961 is a deficient number, since it is larger than the sum of its proper divisors (100295).

155961 is a wasteful number, since it uses less digits than its factorization.

155961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 90 counting only the distinct ones).

The product of its digits is 1350, while the sum is 27.

The square root of 155961 is about 394.9189790324. The cubic root of 155961 is about 53.8276397365.

The spelling of 155961 in words is "one hundred fifty-five thousand, nine hundred sixty-one".