21210857957 has 2 divisors, whose sum is σ = 21210857958. Its totient is φ = 21210857956.

The previous prime is 21210857933. The next prime is 21210857977. The reversal of 21210857957 is 75975801212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10643223556 + 10567634401 = 103166^2 + 102799^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210857957 - 2⁶ = 21210857893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210857977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605428978 + 10605428979.

It is an arithmetic number, because the mean of its divisors is an integer number (10605428979).

Almost surely, 2^21210857957 is an apocalyptic number.

It is an amenable number.

21210857957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210857957 is an equidigital number, since it uses as much as digits as its factorization.

21210857957 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 352800, while the sum is 47.

The spelling of 21210857957 in words is "twenty-one billion, two hundred ten million, eight hundred fifty-seven thousand, nine hundred fifty-seven".