155661 has 16 divisors (see below), whose sum is σ = 233280. Its totient is φ = 91520.

The previous prime is 155657. The next prime is 155663. The reversal of 155661 is 166551.

It is not a de Polignac number, because 155661 - 2² = 155657 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1705 + ... + 1793.

It is an arithmetic number, because the mean of its divisors is an integer number (14580).

2¹⁵⁵⁶⁶¹ is an apocalyptic number.

155661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

155661 is a deficient number, since it is larger than the sum of its proper divisors (77619).

155661 is a wasteful number, since it uses less digits than its factorization.

155661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156.

The product of its digits is 900, while the sum is 24.

The square root of 155661 is about 394.5389714591. The cubic root of 155661 is about 53.7931040576.

The spelling of 155661 in words is "one hundred fifty-five thousand, six hundred sixty-one".