21620061666 has 24 divisors (see below), whose sum is σ = 53535391104. Its totient is φ = 6177160440.

The previous prime is 21620061641. The next prime is 21620061689. The reversal of 21620061666 is 66616002612.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21620061666.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 85793770 + ... + 85794021.

It is an arithmetic number, because the mean of its divisors is an integer number (2230641296).

Almost surely, 2^21620061666 is an apocalyptic number.

21620061666 is an abundant number, since it is smaller than the sum of its proper divisors (31915329438).

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

21620061666 is a wasteful number, since it uses less digits than its factorization.

21620061666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171587806 (or 171587803 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The spelling of 21620061666 in words is "twenty-one billion, six hundred twenty million, sixty-one thousand, six hundred sixty-six".