639494778 has 16 divisors (see below), whose sum is σ = 1377373536. Its totient is φ = 196767600.

The previous prime is 639494749. The next prime is 639494789. The reversal of 639494778 is 877494936.

It is a Curzon number.

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 7 ways as a sum of consecutive naturals, for example, 4099248 + ... + 4099403.

It is an arithmetic number, because the mean of its divisors is an integer number (86085846).

Almost surely, 2^639494778 is an apocalyptic number.

639494778 is an abundant number, since it is smaller than the sum of its proper divisors (737878758).

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

639494778 is a wasteful number, since it uses less digits than its factorization.

639494778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8198669.

The product of its digits is 9144576, while the sum is 57.

The square root of 639494778 is about 25288.2339834161. The cubic root of 639494778 is about 861.5470521910.

The spelling of 639494778 in words is "six hundred thirty-nine million, four hundred ninety-four thousand, seven hundred seventy-eight".