21993764 has 24 divisors (see below), whose sum is σ = 41583360. Its totient is φ = 10118304.

The previous prime is 21993757. The next prime is 21993779. The reversal of 21993764 is 46739912.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24467 + ... + 25349.

It is an arithmetic number, because the mean of its divisors is an integer number (1732640).

Almost surely, 2^21993764 is an apocalyptic number.

It is an amenable number.

21993764 is a deficient number, since it is larger than the sum of its proper divisors (19589596).

21993764 is a wasteful number, since it uses less digits than its factorization.

21993764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1379 (or 1377 counting only the distinct ones).

The product of its digits is 81648, while the sum is 41.

The square root of 21993764 is about 4689.7509528759. The cubic root of 21993764 is about 280.1774555375.

The spelling of 21993764 in words is "twenty-one million, nine hundred ninety-three thousand, seven hundred sixty-four".