638144640 has 768 divisors, whose sum is σ = 2864160000. Its totient is φ = 130056192.

The previous prime is 638144599. The next prime is 638144651. The reversal of 638144640 is 46441836.

638144640 is a `hidden beast` number, since 6 + 3 + 8 + 1 + 4 + 4 + 640 = 666.

It is a super-3 number, since 3×638144640³ (a number of 27 digits) contains 333 as substring.

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 = 638144595 and 638144604.

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, 33586551 + ... + 33586569.

It is an arithmetic number, because the mean of its divisors is an integer number (3729375).

Almost surely, 2^638144640 is an apocalyptic number.

638144640 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 638144640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1432080000).

638144640 is an abundant number, since it is smaller than the sum of its proper divisors (2226015360).

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

638144640 is a wasteful number, since it uses less digits than its factorization.

638144640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 53 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 36.

The square root of 638144640 is about 25261.5248945902. The cubic root of 638144640 is about 860.9403091675.

The spelling of 638144640 in words is "six hundred thirty-eight million, one hundred forty-four thousand, six hundred forty".