21315718 has 16 divisors (see below), whose sum is σ = 32654160. Its totient is φ = 10432800.

The previous prime is 21315709. The next prime is 21315719. The reversal of 21315718 is 81751312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315719) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 46008 + ... + 46468.

It is an arithmetic number, because the mean of its divisors is an integer number (2040885).

Almost surely, 2^21315718 is an apocalyptic number.

21315718 is a deficient number, since it is larger than the sum of its proper divisors (11338442).

21315718 is a wasteful number, since it uses less digits than its factorization.

21315718 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 903.

The product of its digits is 1680, while the sum is 28.

The square root of 21315718 is about 4616.8948439400. The cubic root of 21315718 is about 277.2681525326.

It can be divided in two parts, 213 and 15718, that added together give a triangular number (15931 = T₁₇₈).

The spelling of 21315718 in words is "twenty-one million, three hundred fifteen thousand, seven hundred eighteen".