640139920 has 120 divisors (see below), whose sum is σ = 1755818424. Its totient is φ = 216373248.

The previous prime is 640139893. The next prime is 640139999. The reversal of 640139920 is 29931046.

It can be written as a sum of positive squares in 4 ways, for example, as 154554624 + 485585296 = 12432^2 + 22036^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 285042 + ... + 287278.

Almost surely, 2^640139920 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640139920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (877909212).

640139920 is an abundant number, since it is smaller than the sum of its proper divisors (1115678504).

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

640139920 is a wasteful number, since it uses less digits than its factorization.

640139920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2337 (or 2324 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 34.

The square root of 640139920 is about 25300.9865420303. The cubic root of 640139920 is about 861.8366732078.

The spelling of 640139920 in words is "six hundred forty million, one hundred thirty-nine thousand, nine hundred twenty".