638295920640 has 936 divisors, whose sum is σ = 2663552984040. Its totient is φ = 140807503872.

The previous prime is 638295920623. The next prime is 638295920747. The reversal of 638295920640 is 46029592836.

It is a happy number.

638295920640 is a `hidden beast` number, since 6 + 3 + 8 + 2 + 9 + 592 + 0 + 6 + 40 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 206363049984 + 431932870656 = 454272^2 + 657216^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 261917502 + ... + 261919938.

It is an arithmetic number, because the mean of its divisors is an integer number (2845676265).

Almost surely, 2^638295920640 is an apocalyptic number.

638295920640 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 638295920640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1331776492020).

638295920640 is an abundant number, since it is smaller than the sum of its proper divisors (2025257063400).

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

638295920640 is a wasteful number, since it uses less digits than its factorization.

638295920640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2515 (or 2483 counting only the distinct ones).

The product of its (nonzero) digits is 5598720, while the sum is 54.

The spelling of 638295920640 in words is "six hundred thirty-eight billion, two hundred ninety-five million, nine hundred twenty thousand, six hundred forty".