640450640 has 80 divisors (see below), whose sum is σ = 1568792448. Its totient is φ = 242677248.

The previous prime is 640450637. The next prime is 640450661. The reversal of 640450640 is 46054046.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 195254 + ... + 198506.

Almost surely, 2^640450640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640450640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (784396224).

640450640 is an abundant number, since it is smaller than the sum of its proper divisors (928341808).

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

640450640 is a wasteful number, since it uses less digits than its factorization.

640450640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3396 (or 3390 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 29.

The square root of 640450640 is about 25307.1262690966. The cubic root of 640450640 is about 861.9760940681.

The spelling of 640450640 in words is "six hundred forty million, four hundred fifty thousand, six hundred forty".