21819664 has 20 divisors (see below), whose sum is σ = 42584080. Its totient is φ = 10830240.

The previous prime is 21819659. The next prime is 21819673. The reversal of 21819664 is 46691812.

It is a happy number.

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, 2682 + ... + 7129.

It is an arithmetic number, because the mean of its divisors is an integer number (2129204).

Almost surely, 2^21819664 is an apocalyptic number.

It is an amenable number.

21819664 is a deficient number, since it is larger than the sum of its proper divisors (20764416).

21819664 is a wasteful number, since it uses less digits than its factorization.

21819664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9958 (or 9952 counting only the distinct ones).

The product of its digits is 20736, while the sum is 37.

The square root of 21819664 is about 4671.1523203595. The cubic root of 21819664 is about 279.4362124995.

The spelling of 21819664 in words is "twenty-one million, eight hundred nineteen thousand, six hundred sixty-four".