21205265625 has 84 divisors (see below), whose sum is σ = 38691770364. Its totient is φ = 11190000000.

The previous prime is 21205265597. The next prime is 21205265663. The reversal of 21205265625 is 52656250212.

21205265625 is a `hidden beast` number, since 2 + 1 + 2 + 0 + 5 + 26 + 5 + 625 = 666.

It can be written as a sum of positive squares in 14 ways, for example, as 21076942041 + 128323584 = 145179^2 + 11328^2 .

It is not a de Polignac number, because 21205265625 - 2⁸ = 21205265369 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21205265625.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 14202379 + ... + 14203871.

Almost surely, 2^21205265625 is an apocalyptic number.

21205265625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21205265625 is a deficient number, since it is larger than the sum of its proper divisors (17486504739).

21205265625 is an equidigital number, since it uses as much as digits as its factorization.

21205265625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1630 (or 1602 counting only the distinct ones).

The product of its (nonzero) digits is 72000, while the sum is 36.

The spelling of 21205265625 in words is "twenty-one billion, two hundred five million, two hundred sixty-five thousand, six hundred twenty-five".