640999128 has 128 divisors (see below), whose sum is σ = 2032128000. Its totient is φ = 163643520.

The previous prime is 640999111. The next prime is 640999133. The reversal of 640999128 is 821999046.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 106093 + ... + 111971.

It is an arithmetic number, because the mean of its divisors is an integer number (15876000).

Almost surely, 2^640999128 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 640999128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1016064000).

640999128 is an abundant number, since it is smaller than the sum of its proper divisors (1391128872).

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

640999128 is a wasteful number, since it uses less digits than its factorization.

640999128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5965 (or 5961 counting only the distinct ones).

The product of its (nonzero) digits is 279936, while the sum is 48.

The square root of 640999128 is about 25317.9605813738. The cubic root of 640999128 is about 862.2220920228. Note that the first 3 decimals are identical.

The spelling of 640999128 in words is "six hundred forty million, nine hundred ninety-nine thousand, one hundred twenty-eight".