638244864 has 144 divisors (see below), whose sum is σ = 1904535360. Its totient is φ = 205701120.

The previous prime is 638244863. The next prime is 638244869. The reversal of 638244864 is 468442836.

638244864 is a `hidden beast` number, since 638 + 2 + 4 + 4 + 8 + 6 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638244863) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 570834 + ... + 571950.

It is an arithmetic number, because the mean of its divisors is an integer number (13225940).

Almost surely, 2^638244864 is an apocalyptic number.

638244864 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 638244864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (952267680).

638244864 is an abundant number, since it is smaller than the sum of its proper divisors (1266290496).

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

638244864 is a wasteful number, since it uses less digits than its factorization.

638244864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1176 (or 1153 counting only the distinct ones).

The product of its digits is 884736, while the sum is 45.

The square root of 638244864 is about 25263.5085449349. The cubic root of 638244864 is about 860.9853785552.

The spelling of 638244864 in words is "six hundred thirty-eight million, two hundred forty-four thousand, eight hundred sixty-four".