21147564 has 12 divisors (see below), whose sum is σ = 49344344. Its totient is φ = 7049184.

The previous prime is 21147559. The next prime is 21147593. The reversal of 21147564 is 46574112.

It is a tau number, because it is divible by the number of its divisors (12).

It is an unprimeable number.

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, 881137 + ... + 881160.

Almost surely, 2^21147564 is an apocalyptic number.

It is an amenable number.

21147564 is an abundant number, since it is smaller than the sum of its proper divisors (28196780).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21147564 is a wasteful number, since it uses less digits than its factorization.

21147564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1762304 (or 1762302 counting only the distinct ones).

The product of its digits is 6720, while the sum is 30.

The square root of 21147564 is about 4598.6480622026. The cubic root of 21147564 is about 276.5371287588.

The spelling of 21147564 in words is "twenty-one million, one hundred forty-seven thousand, five hundred sixty-four".