21572731861 has 2 divisors, whose sum is σ = 21572731862. Its totient is φ = 21572731860.

The previous prime is 21572731811. The next prime is 21572731867. The reversal of 21572731861 is 16813727512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18777494961 + 2795236900 = 137031^2 + 52870^2 .

It is a cyclic number.

It is not a de Polignac number, because 21572731861 - 2²⁹ = 21035860949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21572731867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10786365930 + 10786365931.

It is an arithmetic number, because the mean of its divisors is an integer number (10786365931).

Almost surely, 2^21572731861 is an apocalyptic number.

It is an amenable number.

21572731861 is a deficient number, since it is larger than the sum of its proper divisors (1).

21572731861 is an equidigital number, since it uses as much as digits as its factorization.

21572731861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 43.

The spelling of 21572731861 in words is "twenty-one billion, five hundred seventy-two million, seven hundred thirty-one thousand, eight hundred sixty-one".