155861 has 2 divisors, whose sum is σ = 155862. Its totient is φ = 155860.

The previous prime is 155851. The next prime is 155863. The reversal of 155861 is 168551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 155236 + 625 = 394^2 + 25^2 .

It is a cyclic number.

It is not a de Polignac number, because 155861 - 2⁶ = 155797 is a prime.

Together with 155863, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 155861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77930 + 77931.

It is an arithmetic number, because the mean of its divisors is an integer number (77931).

2¹⁵⁵⁸⁶¹ is an apocalyptic number.

It is an amenable number.

155861 is a deficient number, since it is larger than the sum of its proper divisors (1).

155861 is an equidigital number, since it uses as much as digits as its factorization.

155861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1200, while the sum is 26.

The square root of 155861 is about 394.7923504831. The cubic root of 155861 is about 53.8161327682.

The spelling of 155861 in words is "one hundred fifty-five thousand, eight hundred sixty-one".