640673280 has 640 divisors, whose sum is σ = 2639831040. Its totient is φ = 145981440.

The previous prime is 640673273. The next prime is 640673323. The reversal of 640673280 is 82376046.

640673280 is a `hidden beast` number, since 640 + 6 + 7 + 3 + 2 + 8 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 20666865 + ... + 20666895.

It is an arithmetic number, because the mean of its divisors is an integer number (4124736).

Almost surely, 2^640673280 is an apocalyptic number.

640673280 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 640673280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1319915520).

640673280 is an abundant number, since it is smaller than the sum of its proper divisors (1999157760).

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

640673280 is a wasteful number, since it uses less digits than its factorization.

640673280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99 (or 77 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 36.

The square root of 640673280 is about 25311.5246478753. The cubic root of 640673280 is about 862.0759654773.

The spelling of 640673280 in words is "six hundred forty million, six hundred seventy-three thousand, two hundred eighty".