21564851 has 12 divisors (see below), whose sum is σ = 27366840. Its totient is φ = 16803360.

The previous prime is 21564793. The next prime is 21564929. The reversal of 21564851 is 15846512.

It is not a de Polignac number, because 21564851 - 2⁶ = 21564787 is a prime.

It is a Duffinian number.

21564851 is a modest number, since divided by 4851 gives 2156 as remainder.

It is not an unprimeable number, because it can be changed into a prime (21561851) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19466 + ... + 20543.

It is an arithmetic number, because the mean of its divisors is an integer number (2280570).

Almost surely, 2^21564851 is an apocalyptic number.

21564851 is a deficient number, since it is larger than the sum of its proper divisors (5801989).

21564851 is a wasteful number, since it uses less digits than its factorization.

21564851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40034 (or 40027 counting only the distinct ones).

The product of its digits is 9600, while the sum is 32.

The square root of 21564851 is about 4643.7970455221. The cubic root of 21564851 is about 278.3441857753.

It can be divided in two parts, 2156 and 4851, that multiplied together give a square (10458756 = 3234²).

The spelling of 21564851 in words is "twenty-one million, five hundred sixty-four thousand, eight hundred fifty-one".