21680931 has 8 divisors (see below), whose sum is σ = 29018880. Its totient is φ = 14398472.

The previous prime is 21680921. The next prime is 21680947. The reversal of 21680931 is 13908612.

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 21680931 - 2⁹ = 21680419 is a prime.

It is a super-2 number, since 2×21680931² = 940125538053522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21680921) 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, 12951 + ... + 14528.

It is an arithmetic number, because the mean of its divisors is an integer number (3627360).

Almost surely, 2^21680931 is an apocalyptic number.

21680931 is a deficient number, since it is larger than the sum of its proper divisors (7337949).

21680931 is a wasteful number, since it uses less digits than its factorization.

21680931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27745.

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 21680931 is about 4656.2786643413. The cubic root of 21680931 is about 278.8427191274.

The spelling of 21680931 in words is "twenty-one million, six hundred eighty thousand, nine hundred thirty-one".