21566216642 has 8 divisors (see below), whose sum is σ = 32357865036. Its totient is φ = 10780261632.

The previous prime is 21566216599. The next prime is 21566216699. The reversal of 21566216642 is 24661266512.

It can be written as a sum of positive squares in 2 ways, for example, as 21415688281 + 150528361 = 146341^2 + 12269^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 21566216642.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1413863 + ... + 1429034.

Almost surely, 2^21566216642 is an apocalyptic number.

21566216642 is a deficient number, since it is larger than the sum of its proper divisors (10791648394).

21566216642 is a wasteful number, since it uses less digits than its factorization.

21566216642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2846692.

The product of its digits is 207360, while the sum is 41.

The spelling of 21566216642 in words is "twenty-one billion, five hundred sixty-six million, two hundred sixteen thousand, six hundred forty-two".