21057513 has 16 divisors (see below), whose sum is σ = 28723200. Its totient is φ = 13718160.

The previous prime is 21057511. The next prime is 21057521. The reversal of 21057513 is 31575012.

It is not a de Polignac number, because 21057513 - 2¹ = 21057511 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21057511) 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 in 15 ways as a sum of consecutive naturals, for example, 47748 + ... + 48186.

It is an arithmetic number, because the mean of its divisors is an integer number (1795200).

Almost surely, 2^21057513 is an apocalyptic number.

It is an amenable number.

21057513 is a deficient number, since it is larger than the sum of its proper divisors (7665687).

21057513 is a wasteful number, since it uses less digits than its factorization.

21057513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 772.

The product of its (nonzero) digits is 1050, while the sum is 24.

The square root of 21057513 is about 4588.8465871066. The cubic root of 21057513 is about 276.1440515618.

The spelling of 21057513 in words is "twenty-one million, fifty-seven thousand, five hundred thirteen".