640426256 has 40 divisors (see below), whose sum is σ = 1286268120. Its totient is φ = 308532224.

The previous prime is 640426223. The next prime is 640426307. The reversal of 640426256 is 652624046.

It can be written as a sum of positive squares in 4 ways, for example, as 40960000 + 599466256 = 6400^2 + 24484^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 285170 + ... + 287406.

It is an arithmetic number, because the mean of its divisors is an integer number (32156703).

Almost surely, 2^640426256 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 640426256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (643134060).

640426256 is an abundant number, since it is smaller than the sum of its proper divisors (645841864).

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

640426256 is a wasteful number, since it uses less digits than its factorization.

640426256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2891 (or 2885 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 35.

The square root of 640426256 is about 25306.6445029759. The cubic root of 640426256 is about 861.9651545355.

The spelling of 640426256 in words is "six hundred forty million, four hundred twenty-six thousand, two hundred fifty-six".