21751564 has 12 divisors (see below), whose sum is σ = 38191384. Its totient is φ = 10839744.

The previous prime is 21751559. The next prime is 21751567. The reversal of 21751564 is 46515712.

It is a hoax number, since the sum of its digits (31) 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 (21751567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7629 + ... + 10084.

Almost surely, 2^21751564 is an apocalyptic number.

It is an amenable number.

21751564 is a deficient number, since it is larger than the sum of its proper divisors (16439820).

21751564 is a wasteful number, since it uses less digits than its factorization.

21751564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18024 (or 18022 counting only the distinct ones).

The product of its digits is 8400, while the sum is 31.

The square root of 21751564 is about 4663.8572019306. The cubic root of 21751564 is about 279.1451991908.

The spelling of 21751564 in words is "twenty-one million, seven hundred fifty-one thousand, five hundred sixty-four".