640256021436 has 24 divisors (see below), whose sum is σ = 1581808994640. Its totient is φ = 200864634112.

The previous prime is 640256021413. The next prime is 640256021507. The reversal of 640256021436 is 634120652046.

640256021436 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 640256021394 and 640256021403.

It is a congruent number.

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, 1569254751 + ... + 1569255158.

It is an arithmetic number, because the mean of its divisors is an integer number (65908708110).

Almost surely, 2^640256021436 is an apocalyptic number.

It is an amenable number.

640256021436 is an abundant number, since it is smaller than the sum of its proper divisors (941552973204).

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

640256021436 is a wasteful number, since it uses less digits than its factorization.

640256021436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3138509933 (or 3138509931 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 39.

The spelling of 640256021436 in words is "six hundred forty billion, two hundred fifty-six million, twenty-one thousand, four hundred thirty-six".