640634436 has 72 divisors (see below), whose sum is σ = 1770065024. Its totient is φ = 194166720.

The previous prime is 640634417. The next prime is 640634453. The reversal of 640634436 is 634436046.

640634436 is a `hidden beast` number, since 640 + 6 + 3 + 4 + 4 + 3 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 640634436.

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, 21141 + ... + 41571.

Almost surely, 2^640634436 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 640634436, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (885032512).

640634436 is an abundant number, since it is smaller than the sum of its proper divisors (1129430588).

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

640634436 is a wasteful number, since it uses less digits than its factorization.

640634436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20521 (or 20516 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 36.

The square root of 640634436 is about 25310.7573177888. The cubic root of 640634436 is about 862.0585425793.

The spelling of 640634436 in words is "six hundred forty million, six hundred thirty-four thousand, four hundred thirty-six".