638631936 has 180 divisors, whose sum is σ = 1901534544. Its totient is φ = 206438400.

The previous prime is 638631919. The next prime is 638631937. The reversal of 638631936 is 639136836.

638631936 is a `hidden beast` number, since 6 + 3 + 8 + 631 + 9 + 3 + 6 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 638631891 and 638631900.

It is not an unprimeable number, because it can be changed into a prime (638631937) 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, 8994781 + ... + 8994851.

Almost surely, 2^638631936 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638631936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (950767272).

638631936 is an abundant number, since it is smaller than the sum of its proper divisors (1262902608).

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

638631936 is an equidigital number, since it uses as much as digits as its factorization.

638631936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166 (or 137 counting only the distinct ones).

The product of its digits is 419904, while the sum is 45.

The square root of 638631936 is about 25271.1680774752. The cubic root of 638631936 is about 861.1593953541.

The spelling of 638631936 in words is "six hundred thirty-eight million, six hundred thirty-one thousand, nine hundred thirty-six".