21157665255 has 12 divisors (see below), whose sum is σ = 36673286520. Its totient is φ = 11284088112.

The previous prime is 21157665233. The next prime is 21157665257. The reversal of 21157665255 is 55256675112.

21157665255 is a `hidden beast` number, since 2 + 11 + 57 + 66 + 525 + 5 = 666.

It is not a de Polignac number, because 21157665255 - 2⁸ = 21157664999 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 470170339 = 21157665255 / (2 + 1 + 1 + 5 + 7 + 6 + 6 + 5 + 2 + 5 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 21157665255.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157665257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 235085125 + ... + 235085214.

It is an arithmetic number, because the mean of its divisors is an integer number (3056107210).

Almost surely, 2^21157665255 is an apocalyptic number.

21157665255 is a deficient number, since it is larger than the sum of its proper divisors (15515621265).

21157665255 is a wasteful number, since it uses less digits than its factorization.

21157665255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 470170350 (or 470170347 counting only the distinct ones).

The product of its digits is 630000, while the sum is 45.

The spelling of 21157665255 in words is "twenty-one billion, one hundred fifty-seven million, six hundred sixty-five thousand, two hundred fifty-five".