21529957 has 2 divisors, whose sum is σ = 21529958. Its totient is φ = 21529956.

The previous prime is 21529931. The next prime is 21529979. The reversal of 21529957 is 75992512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21215236 + 314721 = 4606^2 + 561^2 .

It is a cyclic number.

It is not a de Polignac number, because 21529957 - 2¹⁹ = 21005669 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21529927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10764978 + 10764979.

It is an arithmetic number, because the mean of its divisors is an integer number (10764979).

Almost surely, 2^21529957 is an apocalyptic number.

It is an amenable number.

21529957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21529957 is an equidigital number, since it uses as much as digits as its factorization.

21529957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56700, while the sum is 40.

The square root of 21529957 is about 4640.0384696681. The cubic root of 21529957 is about 278.1939755197.

The spelling of 21529957 in words is "twenty-one million, five hundred twenty-nine thousand, nine hundred fifty-seven".