21487715 has 16 divisors (see below), whose sum is σ = 26373600. Its totient is φ = 16803072.

The previous prime is 21487709. The next prime is 21487717. The reversal of 21487715 is 51778412.

It is a cyclic number.

It is not a de Polignac number, because 21487715 - 2⁴ = 21487699 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21487717) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48284 + ... + 48726.

It is an arithmetic number, because the mean of its divisors is an integer number (1648350).

Almost surely, 2^21487715 is an apocalyptic number.

21487715 is a deficient number, since it is larger than the sum of its proper divisors (4885885).

21487715 is a wasteful number, since it uses less digits than its factorization.

21487715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646.

The product of its digits is 15680, while the sum is 35.

The square root of 21487715 is about 4635.4843328394. The cubic root of 21487715 is about 278.0119165742.

The spelling of 21487715 in words is "twenty-one million, four hundred eighty-seven thousand, seven hundred fifteen".