21808631 has 8 divisors (see below), whose sum is σ = 23531760. Its totient is φ = 20092032.

The previous prime is 21808621. The next prime is 21808681. The reversal of 21808631 is 13680812.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21808631 is a prime.

It is a super-2 number, since 2×21808631² = 951232772188322, 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 = 21808594 and 21808603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21808621) 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, 7055 + ... + 9663.

It is an arithmetic number, because the mean of its divisors is an integer number (2941470).

Almost surely, 2^21808631 is an apocalyptic number.

21808631 is a deficient number, since it is larger than the sum of its proper divisors (1723129).

21808631 is a wasteful number, since it uses less digits than its factorization.

21808631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3265.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21808631 is about 4669.9711990547. The cubic root of 21808631 is about 279.3891060681.

The spelling of 21808631 in words is "twenty-one million, eight hundred eight thousand, six hundred thirty-one".