21666570 has 32 divisors (see below), whose sum is σ = 52885440. Its totient is φ = 5679360.

The previous prime is 21666563. The next prime is 21666583. The reversal of 21666570 is 7566612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4351 + ... + 7890.

It is an arithmetic number, because the mean of its divisors is an integer number (1652670).

Almost surely, 2^21666570 is an apocalyptic number.

21666570 is an abundant number, since it is smaller than the sum of its proper divisors (31218870).

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

21666570 is a wasteful number, since it uses less digits than its factorization.

21666570 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12310.

The product of its (nonzero) digits is 15120, while the sum is 33.

The square root of 21666570 is about 4654.7362975791. The cubic root of 21666570 is about 278.7811389801.

The spelling of 21666570 in words is "twenty-one million, six hundred sixty-six thousand, five hundred seventy".