642220817818 has 24 divisors (see below), whose sum is σ = 997934582268. Its totient is φ = 309963187968.

The previous prime is 642220817807. The next prime is 642220817857. The reversal of 642220817818 is 818718022246.

It can be written as a sum of positive squares in 6 ways, for example, as 188231896449 + 453988921369 = 433857^2 + 673787^2 .

It is a super-2 number, since 2×642220817818² (a number of 24 digits) contains 22 as substring.

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, 7311730 + ... + 7399042.

Almost surely, 2^642220817818 is an apocalyptic number.

642220817818 is a deficient number, since it is larger than the sum of its proper divisors (355713764450).

642220817818 is a wasteful number, since it uses less digits than its factorization.

642220817818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91746 (or 91717 counting only the distinct ones).

The product of its (nonzero) digits is 688128, while the sum is 49.

The spelling of 642220817818 in words is "six hundred forty-two billion, two hundred twenty million, eight hundred seventeen thousand, eight hundred eighteen".