21665570 has 8 divisors (see below), whose sum is σ = 38998044. Its totient is φ = 8666224.

The previous prime is 21665569. The next prime is 21665587. The reversal of 21665570 is 7556612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21077281 + 588289 = 4591^2 + 767^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

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 3 ways as a sum of consecutive naturals, for example, 1083269 + ... + 1083288.

Almost surely, 2^21665570 is an apocalyptic number.

21665570 is a deficient number, since it is larger than the sum of its proper divisors (17332474).

21665570 is a wasteful number, since it uses less digits than its factorization.

21665570 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2166564.

The product of its (nonzero) digits is 12600, while the sum is 32.

The square root of 21665570 is about 4654.6288788689. The cubic root of 21665570 is about 278.7768499544.

The spelling of 21665570 in words is "twenty-one million, six hundred sixty-five thousand, five hundred seventy".