21065566 has 16 divisors (see below), whose sum is σ = 33667200. Its totient is φ = 9856728.

The previous prime is 21065563. The next prime is 21065599. The reversal of 21065566 is 66556012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 186 + ... + 6493.

It is an arithmetic number, because the mean of its divisors is an integer number (2104200).

Almost surely, 2^21065566 is an apocalyptic number.

21065566 is a deficient number, since it is larger than the sum of its proper divisors (12601634).

21065566 is a wasteful number, since it uses less digits than its factorization.

21065566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6783.

The product of its (nonzero) digits is 10800, while the sum is 31.

The square root of 21065566 is about 4589.7239568410. The cubic root of 21065566 is about 276.1792488906.

The spelling of 21065566 in words is "twenty-one million, sixty-five thousand, five hundred sixty-six".