21644684 has 6 divisors (see below), whose sum is σ = 37878204. Its totient is φ = 10822340.

The previous prime is 21644669. The next prime is 21644687. The reversal of 21644684 is 48644612.

It is not an unprimeable number, because it can be changed into a prime (21644687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2705582 + ... + 2705589.

It is an arithmetic number, because the mean of its divisors is an integer number (6313034).

Almost surely, 2^21644684 is an apocalyptic number.

It is an amenable number.

21644684 is a deficient number, since it is larger than the sum of its proper divisors (16233520).

21644684 is a wasteful number, since it uses less digits than its factorization.

21644684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5411175 (or 5411173 counting only the distinct ones).

The product of its digits is 36864, while the sum is 35.

The square root of 21644684 is about 4652.3847648276. The cubic root of 21644684 is about 278.6872391834.

The spelling of 21644684 in words is "twenty-one million, six hundred forty-four thousand, six hundred eighty-four".