21437644 has 12 divisors (see below), whose sum is σ = 37585800. Its totient is φ = 10698848.

The previous prime is 21437639. The next prime is 21437701. The reversal of 21437644 is 44673412.

It is a plaindrome in base 11.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2434 + ... + 6985.

It is an arithmetic number, because the mean of its divisors is an integer number (3132150).

Almost surely, 2^21437644 is an apocalyptic number.

It is an amenable number.

21437644 is a deficient number, since it is larger than the sum of its proper divisors (16148156).

21437644 is a wasteful number, since it uses less digits than its factorization.

21437644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9992 (or 9990 counting only the distinct ones).

The product of its digits is 16128, while the sum is 31.

The square root of 21437644 is about 4630.0803448752. The cubic root of 21437644 is about 277.7958060951.

The spelling of 21437644 in words is "twenty-one million, four hundred thirty-seven thousand, six hundred forty-four".