642691656 has 24 divisors (see below), whose sum is σ = 1740623430. Its totient is φ = 214230528.

The previous prime is 642691573. The next prime is 642691697. The reversal of 642691656 is 656196246.

It can be written as a sum of positive squares in only one way, i.e., 437228100 + 205463556 = 20910^2 + 14334^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4463065 + ... + 4463208.

Almost surely, 2^642691656 is an apocalyptic number.

It is an amenable number.

642691656 is an abundant number, since it is smaller than the sum of its proper divisors (1097931774).

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

642691656 is a wasteful number, since it uses less digits than its factorization.

642691656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8926285 (or 8926278 counting only the distinct ones).

The product of its digits is 466560, while the sum is 45.

The square root of 642691656 is about 25351.3639869732. The cubic root of 642691656 is about 862.9803106719.

The spelling of 642691656 in words is "six hundred forty-two million, six hundred ninety-one thousand, six hundred fifty-six".