639735640 has 16 divisors (see below), whose sum is σ = 1439405280. Its totient is φ = 255894240.

The previous prime is 639735637. The next prime is 639735647. The reversal of 639735640 is 46537936.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639735647) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 7996656 + ... + 7996735.

It is an arithmetic number, because the mean of its divisors is an integer number (89962830).

Almost surely, 2^639735640 is an apocalyptic number.

It is an amenable number.

639735640 is an abundant number, since it is smaller than the sum of its proper divisors (799669640).

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

639735640 is a wasteful number, since it uses less digits than its factorization.

639735640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15993402 (or 15993398 counting only the distinct ones).

The product of its (nonzero) digits is 408240, while the sum is 43.

The square root of 639735640 is about 25292.9958684218. The cubic root of 639735640 is about 861.6552041811.

The spelling of 639735640 in words is "six hundred thirty-nine million, seven hundred thirty-five thousand, six hundred forty".