21386731 has 8 divisors (see below), whose sum is σ = 22685184. Its totient is φ = 20092800.

The previous prime is 21386713. The next prime is 21386747. The reversal of 21386731 is 13768312.

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

It is a cyclic number.

It is not a de Polignac number, because 21386731 - 2⁵ = 21386699 is a prime.

It is a super-2 number, since 2×21386731² = 914784525732722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21386693 and 21386702.

It is not an unprimeable number, because it can be changed into a prime (21386791) 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, 18006 + ... + 19156.

It is an arithmetic number, because the mean of its divisors is an integer number (2835648).

Almost surely, 2^21386731 is an apocalyptic number.

21386731 is a deficient number, since it is larger than the sum of its proper divisors (1298453).

21386731 is a wasteful number, since it uses less digits than its factorization.

21386731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2261.

The product of its digits is 6048, while the sum is 31.

The square root of 21386731 is about 4624.5790078666. The cubic root of 21386731 is about 277.5757161568.

The spelling of 21386731 in words is "twenty-one million, three hundred eighty-six thousand, seven hundred thirty-one".