638686464 has 288 divisors, whose sum is σ = 2002662144. Its totient is φ = 178913280.

The previous prime is 638686423. The next prime is 638686483. The reversal of 638686464 is 464686836.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8995549 + ... + 8995619.

It is an arithmetic number, because the mean of its divisors is an integer number (6953688).

Almost surely, 2^638686464 is an apocalyptic number.

638686464 is a gapful number since it is divisible by the number (64) 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 638686464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1001331072).

638686464 is an abundant number, since it is smaller than the sum of its proper divisors (1363975680).

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

638686464 is a wasteful number, since it uses less digits than its factorization.

638686464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173 (or 159 counting only the distinct ones).

The product of its digits is 3981312, while the sum is 51.

The square root of 638686464 is about 25272.2469123741. The cubic root of 638686464 is about 861.1839039746.

The spelling of 638686464 in words is "six hundred thirty-eight million, six hundred eighty-six thousand, four hundred sixty-four".