640243680 has 48 divisors (see below), whose sum is σ = 2016769104. Its totient is φ = 170731520.

The previous prime is 640243679. The next prime is 640243687. The reversal of 640243680 is 86342046.

It is a tau number, because it is divible by the number of its divisors (48).

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640243687) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 666441 + ... + 667400.

It is an arithmetic number, because the mean of its divisors is an integer number (42016023).

Almost surely, 2^640243680 is an apocalyptic number.

640243680 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640243680 is an abundant number, since it is smaller than the sum of its proper divisors (1376525424).

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

640243680 is a wasteful number, since it uses less digits than its factorization.

640243680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1333859 (or 1333851 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 33.

The square root of 640243680 is about 25303.0369718736. The cubic root of 640243680 is about 861.8832356021.

The spelling of 640243680 in words is "six hundred forty million, two hundred forty-three thousand, six hundred eighty".