639968994 has 48 divisors (see below), whose sum is σ = 1586362752. Its totient is φ = 182654784.

The previous prime is 639968969. The next prime is 639968999. The reversal of 639968994 is 499869936.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is not an unprimeable number, because it can be changed into a prime (639968999) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 152022 + ... + 156174.

It is an arithmetic number, because the mean of its divisors is an integer number (33049224).

Almost surely, 2^639968994 is an apocalyptic number.

639968994 is an abundant number, since it is smaller than the sum of its proper divisors (946393758).

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

639968994 is a wasteful number, since it uses less digits than its factorization.

639968994 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5391 (or 5388 counting only the distinct ones).

The product of its digits is 22674816, while the sum is 63.

The square root of 639968994 is about 25297.6084640426. The cubic root of 639968994 is about 861.7599590376.

Adding to 639968994 its product of digits (22674816), we get a triangular number (662643810 = T₃₆₄₀₄).

The spelling of 639968994 in words is "six hundred thirty-nine million, nine hundred sixty-eight thousand, nine hundred ninety-four".