21715021666 has 8 divisors (see below), whose sum is σ = 35078111964. Its totient is φ = 10022317680.

The previous prime is 21715021651. The next prime is 21715021687. The reversal of 21715021666 is 66612051712.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20814121441 + 900900225 = 144271^2 + 30015^2 .

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 (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 417596545 + ... + 417596596.

Almost surely, 2^21715021666 is an apocalyptic number.

21715021666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21715021666 is a deficient number, since it is larger than the sum of its proper divisors (13363090298).

21715021666 is a wasteful number, since it uses less digits than its factorization.

21715021666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 835193156.

The product of its (nonzero) digits is 30240, while the sum is 37.

The spelling of 21715021666 in words is "twenty-one billion, seven hundred fifteen million, twenty-one thousand, six hundred sixty-six".