639777720 has 48 divisors (see below), whose sum is σ = 1920164760. Its totient is φ = 170533504.

The previous prime is 639777689. The next prime is 639777727. The reversal of 639777720 is 27777936.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 639777720.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639777727) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 275926 + ... + 278234.

Almost surely, 2^639777720 is an apocalyptic number.

639777720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

639777720 is an abundant number, since it is smaller than the sum of its proper divisors (1280387040).

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

639777720 is an equidigital number, since it uses as much as digits as its factorization.

639777720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4632 (or 2319 counting only the distinct ones).

The product of its (nonzero) digits is 777924, while the sum is 48.

The square root of 639777720 is about 25293.8277055886. The cubic root of 639777720 is about 861.6740961805.

The spelling of 639777720 in words is "six hundred thirty-nine million, seven hundred seventy-seven thousand, seven hundred twenty".