21157665233 has 2 divisors, whose sum is σ = 21157665234. Its totient is φ = 21157665232.

The previous prime is 21157665229. The next prime is 21157665257. The reversal of 21157665233 is 33256675112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20945904529 + 211760704 = 144727^2 + 14552^2 .

It is a cyclic number.

It is not a de Polignac number, because 21157665233 - 2² = 21157665229 is a prime.

It is a super-2 number, since 2×21157665233² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21157665833) 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, 10578832616 + 10578832617.

It is an arithmetic number, because the mean of its divisors is an integer number (10578832617).

Almost surely, 2^21157665233 is an apocalyptic number.

It is an amenable number.

21157665233 is a deficient number, since it is larger than the sum of its proper divisors (1).

21157665233 is an equidigital number, since it uses as much as digits as its factorization.

21157665233 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 226800, while the sum is 41.

The spelling of 21157665233 in words is "twenty-one billion, one hundred fifty-seven million, six hundred sixty-five thousand, two hundred thirty-three".