640137888 has 144 divisors (see below), whose sum is σ = 2013842376. Its totient is φ = 191600640.

The previous prime is 640137857. The next prime is 640137889. The reversal of 640137888 is 888731046.

It can be written as a sum of positive squares in 4 ways, for example, as 531394704 + 108743184 = 23052^2 + 10428^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is not an unprimeable number, because it can be changed into a prime (640137889) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 136218 + ... + 140838.

Almost surely, 2^640137888 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 640137888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1006921188).

640137888 is an abundant number, since it is smaller than the sum of its proper divisors (1373704488).

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

640137888 is a wasteful number, since it uses less digits than its factorization.

640137888 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4687 (or 4676 counting only the distinct ones).

The product of its (nonzero) digits is 258048, while the sum is 45.

The square root of 640137888 is about 25300.9463854616. The cubic root of 640137888 is about 861.8357612958.

The spelling of 640137888 in words is "six hundred forty million, one hundred thirty-seven thousand, eight hundred eighty-eight".