21051715 has 24 divisors (see below), whose sum is σ = 27157680. Its totient is φ = 15660864.

The previous prime is 21051707. The next prime is 21051721. The reversal of 21051715 is 51715012.

21051715 = 201² + 202² + ... + 414².

It is not a de Polignac number, because 21051715 - 2³ = 21051707 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 193081 + ... + 193189.

It is an arithmetic number, because the mean of its divisors is an integer number (1131570).

Almost surely, 2^21051715 is an apocalyptic number.

21051715 is a deficient number, since it is larger than the sum of its proper divisors (6105965).

21051715 is a wasteful number, since it uses less digits than its factorization.

21051715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 350, while the sum is 22.

The square root of 21051715 is about 4588.2147944489. The cubic root of 21051715 is about 276.1187046277.

Adding to 21051715 its reverse (51715012), we get a palindrome (72766727).

The spelling of 21051715 in words is "twenty-one million, fifty-one thousand, seven hundred fifteen".