640665340 has 48 divisors (see below), whose sum is σ = 1540389312. Its totient is φ = 219257856.

The previous prime is 640665331. The next prime is 640665373. The reversal of 640665340 is 43566046.

It is a junction number, because it is equal to n+sod(n) for n = 640665296 and 640665305.

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, 79162 + ... + 86878.

It is an arithmetic number, because the mean of its divisors is an integer number (32091444).

Almost surely, 2^640665340 is an apocalyptic number.

It is an amenable number.

640665340 is an abundant number, since it is smaller than the sum of its proper divisors (899723972).

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

640665340 is a wasteful number, since it uses less digits than its factorization.

640665340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8326 (or 8324 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 34.

The square root of 640665340 is about 25311.3678018396. The cubic root of 640665340 is about 862.0724041658.

The spelling of 640665340 in words is "six hundred forty million, six hundred sixty-five thousand, three hundred forty".