21047564 has 12 divisors (see below), whose sum is σ = 39000024. Its totient is φ = 9904704.

The previous prime is 21047563. The next prime is 21047567. The reversal of 21047564 is 46574012.

It is not an unprimeable number, because it can be changed into a prime (21047563) 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, 154694 + ... + 154829.

It is an arithmetic number, because the mean of its divisors is an integer number (3250002).

Almost surely, 2^21047564 is an apocalyptic number.

It is an amenable number.

21047564 is a deficient number, since it is larger than the sum of its proper divisors (17952460).

21047564 is a wasteful number, since it uses less digits than its factorization.

21047564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 309544 (or 309542 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 29.

The square root of 21047564 is about 4587.7624175626. The cubic root of 21047564 is about 276.1005549728.

It can be divided in two parts, 210 and 47564, that added together give a palindrome (47774).

The spelling of 21047564 in words is "twenty-one million, forty-seven thousand, five hundred sixty-four".