640721760 has 192 divisors, whose sum is σ = 2363364864. Its totient is φ = 142848000.

The previous prime is 640721759. The next prime is 640721773. The reversal of 640721760 is 67127046.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 135435 + ... + 140085.

It is an arithmetic number, because the mean of its divisors is an integer number (12309192).

Almost surely, 2^640721760 is an apocalyptic number.

640721760 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640721760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1181682432).

640721760 is an abundant number, since it is smaller than the sum of its proper divisors (1722643104).

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

640721760 is a wasteful number, since it uses less digits than its factorization.

640721760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4717 (or 4709 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 33.

The square root of 640721760 is about 25312.4822962901. The cubic root of 640721760 is about 862.0977094717.

The spelling of 640721760 in words is "six hundred forty million, seven hundred twenty-one thousand, seven hundred sixty".