21764564 has 6 divisors (see below), whose sum is σ = 38087994. Its totient is φ = 10882280.

The previous prime is 21764551. The next prime is 21764581. The reversal of 21764564 is 46546712.

It can be written as a sum of positive squares in only one way, i.e., 21696964 + 67600 = 4658^2 + 260^2 .

It is a super-2 number, since 2×21764564² = 947392492220192, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2720567 + ... + 2720574.

It is an arithmetic number, because the mean of its divisors is an integer number (6347999).

Almost surely, 2^21764564 is an apocalyptic number.

It is an amenable number.

21764564 is a deficient number, since it is larger than the sum of its proper divisors (16323430).

21764564 is a wasteful number, since it uses less digits than its factorization.

21764564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5441145 (or 5441143 counting only the distinct ones).

The product of its digits is 40320, while the sum is 35.

The square root of 21764564 is about 4665.2506899415. The cubic root of 21764564 is about 279.2007992522.

The spelling of 21764564 in words is "twenty-one million, seven hundred sixty-four thousand, five hundred sixty-four".