640426320 has 60 divisors (see below), whose sum is σ = 2150767476. Its totient is φ = 170780160.

The previous prime is 640426309. The next prime is 640426349. The reversal of 640426320 is 23624046.

It can be written as a sum of positive squares in 2 ways, for example, as 399680064 + 240746256 = 19992^2 + 15516^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 444021 + ... + 445460.

Almost surely, 2^640426320 is an apocalyptic number.

640426320 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640426320 is an abundant number, since it is smaller than the sum of its proper divisors (1510341156).

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

640426320 is a wasteful number, since it uses less digits than its factorization.

640426320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 889500 (or 889491 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 27.

The square root of 640426320 is about 25306.6457674659. The cubic root of 640426320 is about 861.9651832486.

The spelling of 640426320 in words is "six hundred forty million, four hundred twenty-six thousand, three hundred twenty".