21853665 has 16 divisors (see below), whose sum is σ = 38851200. Its totient is φ = 11655216.

The previous prime is 21853661. The next prime is 21853679. The reversal of 21853665 is 56635812.

It is not a de Polignac number, because 21853665 - 2² = 21853661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21853661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 80805 + ... + 81074.

It is an arithmetic number, because the mean of its divisors is an integer number (2428200).

Almost surely, 2^21853665 is an apocalyptic number.

It is an amenable number.

21853665 is a deficient number, since it is larger than the sum of its proper divisors (16997535).

21853665 is a wasteful number, since it uses less digits than its factorization.

21853665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161893 (or 161887 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 21853665 is about 4674.7903696316. The cubic root of 21853665 is about 279.5812831694.

The spelling of 21853665 in words is "twenty-one million, eight hundred fifty-three thousand, six hundred sixty-five".