21686718 has 16 divisors (see below), whose sum is σ = 43462656. Its totient is φ = 7214040.

The previous prime is 21686671. The next prime is 21686741. The reversal of 21686718 is 81768612.

It is a super-2 number, since 2×21686718² = 940627475223048, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 318 + ... + 6593.

It is an arithmetic number, because the mean of its divisors is an integer number (2716416).

Almost surely, 2^21686718 is an apocalyptic number.

21686718 is an abundant number, since it is smaller than the sum of its proper divisors (21775938).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21686718 is a wasteful number, since it uses less digits than its factorization.

21686718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7439.

The product of its digits is 32256, while the sum is 39.

The square root of 21686718 is about 4656.9000418733. The cubic root of 21686718 is about 278.8675261689.

The spelling of 21686718 in words is "twenty-one million, six hundred eighty-six thousand, seven hundred eighteen".