639512640 has 672 divisors, whose sum is σ = 2662732800. Its totient is φ = 139345920.

The previous prime is 639512591. The next prime is 639512651. The reversal of 639512640 is 46215936.

It is a happy number.

639512640 is a `hidden beast` number, since 6 + 3 + 9 + 5 + 1 + 2 + 640 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 639512595 and 639512604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 20629425 + ... + 20629455.

It is an arithmetic number, because the mean of its divisors is an integer number (3962400).

Almost surely, 2^639512640 is an apocalyptic number.

639512640 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 639512640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1331366400).

639512640 is an abundant number, since it is smaller than the sum of its proper divisors (2023220160).

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

639512640 is a wasteful number, since it uses less digits than its factorization.

639512640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115 (or 102 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 36.

The square root of 639512640 is about 25288.5871491469. The cubic root of 639512640 is about 861.5550735285. Note that the first 3 decimals are identical.

The spelling of 639512640 in words is "six hundred thirty-nine million, five hundred twelve thousand, six hundred forty".