155661616321 has 2 divisors, whose sum is σ = 155661616322. Its totient is φ = 155661616320.

The previous prime is 155661616259. The next prime is 155661616351. The reversal of 155661616321 is 123616166551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151025504400 + 4636111921 = 388620^2 + 68089^2 .

It is a cyclic number.

It is not a de Polignac number, because 155661616321 - 2²⁹ = 155124745409 is a prime.

It is not a weakly prime, because it can be changed into another prime (155661616351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77830808160 + 77830808161.

It is an arithmetic number, because the mean of its divisors is an integer number (77830808161).

Almost surely, 2^155661616321 is an apocalyptic number.

It is an amenable number.

155661616321 is a deficient number, since it is larger than the sum of its proper divisors (1).

155661616321 is an equidigital number, since it uses as much as digits as its factorization.

155661616321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 194400, while the sum is 43.

The spelling of 155661616321 in words is "one hundred fifty-five billion, six hundred sixty-one million, six hundred sixteen thousand, three hundred twenty-one".