21386691 has 12 divisors (see below), whose sum is σ = 31327920. Its totient is φ = 14056560.

The previous prime is 21386689. The next prime is 21386699. The reversal of 21386691 is 19668312.

It is not a de Polignac number, because 21386691 - 2¹ = 21386689 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21386699) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 16096 + ... + 17373.

It is an arithmetic number, because the mean of its divisors is an integer number (2610660).

Almost surely, 2^21386691 is an apocalyptic number.

21386691 is a deficient number, since it is larger than the sum of its proper divisors (9941229).

21386691 is a wasteful number, since it uses less digits than its factorization.

21386691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33546 (or 33543 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 21386691 is about 4624.5746831465. The cubic root of 21386691 is about 277.5755431050.

The spelling of 21386691 in words is "twenty-one million, three hundred eighty-six thousand, six hundred ninety-one".