21634665 has 16 divisors (see below), whose sum is σ = 37278528. Its totient is φ = 10650816.

The previous prime is 21634663. The next prime is 21634699. The reversal of 21634665 is 56643612.

It is not a de Polignac number, because 21634665 - 2¹ = 21634663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21634661) 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, 55279 + ... + 55668.

It is an arithmetic number, because the mean of its divisors is an integer number (2329908).

Almost surely, 2^21634665 is an apocalyptic number.

It is an amenable number.

21634665 is a deficient number, since it is larger than the sum of its proper divisors (15643863).

21634665 is a wasteful number, since it uses less digits than its factorization.

21634665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110968.

The product of its digits is 25920, while the sum is 33.

The square root of 21634665 is about 4651.3078805858. The cubic root of 21634665 is about 278.6442324975.

The spelling of 21634665 in words is "twenty-one million, six hundred thirty-four thousand, six hundred sixty-five".