155691 has 6 divisors (see below), whose sum is σ = 224900. Its totient is φ = 103788.

The previous prime is 155689. The next prime is 155693. The reversal of 155691 is 196551.

It is an interprime number because it is at equal distance from previous prime (155689) and next prime (155693).

It is not a de Polignac number, because 155691 - 2¹ = 155689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (155693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8641 + ... + 8658.

2¹⁵⁵⁶⁹¹ is an apocalyptic number.

155691 is a deficient number, since it is larger than the sum of its proper divisors (69209).

155691 is a wasteful number, since it uses less digits than its factorization.

155691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17305 (or 17302 counting only the distinct ones).

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

The square root of 155691 is about 394.5769886854. The cubic root of 155691 is about 53.7965596212.

The spelling of 155691 in words is "one hundred fifty-five thousand, six hundred ninety-one".