21515713 has 4 divisors (see below), whose sum is σ = 21672900. Its totient is φ = 21358528.

The previous prime is 21515701. The next prime is 21515717. The reversal of 21515713 is 31751512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17783089 + 3732624 = 4217^2 + 1932^2 .

It is a cyclic number.

It is not a de Polignac number, because 21515713 - 2²¹ = 19418561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21515717) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78388 + ... + 78661.

It is an arithmetic number, because the mean of its divisors is an integer number (5418225).

Almost surely, 2^21515713 is an apocalyptic number.

It is an amenable number.

21515713 is a deficient number, since it is larger than the sum of its proper divisors (157187).

21515713 is a wasteful number, since it uses less digits than its factorization.

21515713 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157186.

The product of its digits is 1050, while the sum is 25.

The square root of 21515713 is about 4638.5033146479. The cubic root of 21515713 is about 278.1326118861.

The spelling of 21515713 in words is "twenty-one million, five hundred fifteen thousand, seven hundred thirteen".