639569994 has 64 divisors (see below), whose sum is σ = 1494761472. Its totient is φ = 178660800.

The previous prime is 639569981. The next prime is 639569999. The reversal of 639569994 is 499965936.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (639569999) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 488689 + ... + 489995.

It is an arithmetic number, because the mean of its divisors is an integer number (23355648).

Almost surely, 2^639569994 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639569994, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (747380736).

639569994 is an abundant number, since it is smaller than the sum of its proper divisors (855191478).

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

639569994 is a wasteful number, since it uses less digits than its factorization.

639569994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1571.

The product of its digits is 14171760, while the sum is 60.

The square root of 639569994 is about 25289.7211135275. The cubic root of 639569994 is about 861.5808286371.

The spelling of 639569994 in words is "six hundred thirty-nine million, five hundred sixty-nine thousand, nine hundred ninety-four".