21717764 has 12 divisors (see below), whose sum is σ = 38541888. Its totient is φ = 10705800.

The previous prime is 21717749. The next prime is 21717767. The reversal of 21717764 is 46771712.

It is a super-2 number, since 2×21717764² = 943322546319392, which contains 22 as substring.

It is a hoax number, since the sum of its digits (35) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21717767) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37952 + ... + 38519.

It is an arithmetic number, because the mean of its divisors is an integer number (3211824).

Almost surely, 2^21717764 is an apocalyptic number.

It is an amenable number.

21717764 is a deficient number, since it is larger than the sum of its proper divisors (16824124).

21717764 is a wasteful number, since it uses less digits than its factorization.

21717764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76546 (or 76544 counting only the distinct ones).

The product of its digits is 16464, while the sum is 35.

The square root of 21717764 is about 4660.2321830570. The cubic root of 21717764 is about 279.0005352782. Note that the first 3 decimals are identical.

The spelling of 21717764 in words is "twenty-one million, seven hundred seventeen thousand, seven hundred sixty-four".