21386631 has 8 divisors (see below), whose sum is σ = 32589184. Its totient is φ = 12220920.

The previous prime is 21386623. The next prime is 21386639. The reversal of 21386631 is 13668312.

It is an interprime number because it is at equal distance from previous prime (21386623) and next prime (21386639).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21386631 - 2³ = 21386623 is a prime.

It is a super-2 number, since 2×21386631² = 914775971060322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21386639) 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, 509185 + ... + 509226.

It is an arithmetic number, because the mean of its divisors is an integer number (4073648).

Almost surely, 2^21386631 is an apocalyptic number.

21386631 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21386631 is a deficient number, since it is larger than the sum of its proper divisors (11202553).

21386631 is a wasteful number, since it uses less digits than its factorization.

21386631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1018421.

The product of its digits is 5184, while the sum is 30.

The square root of 21386631 is about 4624.5681960590. The cubic root of 21386631 is about 277.5752835269.

The spelling of 21386631 in words is "twenty-one million, three hundred eighty-six thousand, six hundred thirty-one".