21708687 has 32 divisors (see below), whose sum is σ = 38868480. Its totient is φ = 10408320.

The previous prime is 21708671. The next prime is 21708703. The reversal of 21708687 is 78680712.

It is an interprime number because it is at equal distance from previous prime (21708671) and next prime (21708703).

It is not a de Polignac number, because 21708687 - 2⁴ = 21708671 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21708607) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 612 + ... + 6617.

It is an arithmetic number, because the mean of its divisors is an integer number (1214640).

Almost surely, 2^21708687 is an apocalyptic number.

21708687 is a deficient number, since it is larger than the sum of its proper divisors (17159793).

21708687 is a wasteful number, since it uses less digits than its factorization.

21708687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7263.

The product of its (nonzero) digits is 37632, while the sum is 39.

The square root of 21708687 is about 4659.2582027615. The cubic root of 21708687 is about 278.9616601779.

The spelling of 21708687 in words is "twenty-one million, seven hundred eight thousand, six hundred eighty-seven".