21808336 has 20 divisors (see below), whose sum is σ = 46095264. Its totient is φ = 9912800.

The previous prime is 21808321. The next prime is 21808337. The reversal of 21808336 is 63380812.

It is a junction number, because it is equal to n+sod(n) for n = 21808298 and 21808307.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21808337) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61780 + ... + 62131.

Almost surely, 2^21808336 is an apocalyptic number.

It is an amenable number.

21808336 is an abundant number, since it is smaller than the sum of its proper divisors (24286928).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21808336 is a wasteful number, since it uses less digits than its factorization.

21808336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123930 (or 123924 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 21808336 is about 4669.9396141706. The cubic root of 21808336 is about 279.3878463198.

The spelling of 21808336 in words is "twenty-one million, eight hundred eight thousand, three hundred thirty-six".