638657187840 has 1404 divisors, whose sum is σ = 2701645360596. Its totient is φ = 144473849856.

The previous prime is 638657187827. The next prime is 638657187859. The reversal of 638657187840 is 48781756836.

It can be written as a sum of positive squares in 2 ways, for example, as 258096513024 + 380560674816 = 508032^2 + 616896^2 .

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 6584094672 + ... + 6584094768.

Almost surely, 2^638657187840 is an apocalyptic number.

638657187840 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 638657187840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1350822680298).

638657187840 is an abundant number, since it is smaller than the sum of its proper divisors (2062988172756).

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

638657187840 is an frugal number, since it uses more digits than its factorization.

638657187840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164 (or 114 counting only the distinct ones).

The product of its (nonzero) digits is 54190080, while the sum is 63.

The spelling of 638657187840 in words is "six hundred thirty-eight billion, six hundred fifty-seven million, one hundred eighty-seven thousand, eight hundred forty".