21657594557 has 2 divisors, whose sum is σ = 21657594558. Its totient is φ = 21657594556.

The previous prime is 21657594547. The next prime is 21657594583. The reversal of 21657594557 is 75549575612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19436263396 + 2221331161 = 139414^2 + 47131^2 .

It is a cyclic number.

It is not a de Polignac number, because 21657594557 - 2¹⁸ = 21657332413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21657594547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828797278 + 10828797279.

It is an arithmetic number, because the mean of its divisors is an integer number (10828797279).

Almost surely, 2^21657594557 is an apocalyptic number.

It is an amenable number.

21657594557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657594557 is an equidigital number, since it uses as much as digits as its factorization.

21657594557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13230000, while the sum is 56.

The spelling of 21657594557 in words is "twenty-one billion, six hundred fifty-seven million, five hundred ninety-four thousand, five hundred fifty-seven".