638655120840 has 128 divisors (see below), whose sum is σ = 2090501913600. Its totient is φ = 154798974720.

The previous prime is 638655120839. The next prime is 638655120841. The reversal of 638655120840 is 48021556836.

It is a happy number.

638655120840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (638655120839) and next prime (638655120841).

It is a self number, because there is not a number n which added to its sum of digits gives 638655120840.

It is not an unprimeable number, because it can be changed into a prime (638655120841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8308101 + ... + 8384619.

It is an arithmetic number, because the mean of its divisors is an integer number (16332046200).

Almost surely, 2^638655120840 is an apocalyptic number.

638655120840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

638655120840 is an abundant number, since it is smaller than the sum of its proper divisors (1451846792760).

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

638655120840 is a wasteful number, since it uses less digits than its factorization.

638655120840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82867 (or 82863 counting only the distinct ones).

The product of its (nonzero) digits is 1382400, while the sum is 48.

The spelling of 638655120840 in words is "six hundred thirty-eight billion, six hundred fifty-five million, one hundred twenty thousand, eight hundred forty".