638523918 has 64 divisors (see below), whose sum is σ = 1500595200. Its totient is φ = 200698560.

The previous prime is 638523917. The next prime is 638523923. The reversal of 638523918 is 819325836.

It is a happy number.

638523918 is a `hidden beast` number, since 6 + 38 + 523 + 91 + 8 = 666.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638523917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 237723 + ... + 240393.

It is an arithmetic number, because the mean of its divisors is an integer number (23446800).

Almost surely, 2^638523918 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638523918, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (750297600).

638523918 is an abundant number, since it is smaller than the sum of its proper divisors (862071282).

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

638523918 is a wasteful number, since it uses less digits than its factorization.

638523918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2934 (or 2928 counting only the distinct ones).

The product of its digits is 311040, while the sum is 45.

The square root of 638523918 is about 25269.0308084818. The cubic root of 638523918 is about 861.1108405423.

It can be divided in two parts, 6385 and 23918, that added together give a palindrome (30303).

The spelling of 638523918 in words is "six hundred thirty-eight million, five hundred twenty-three thousand, nine hundred eighteen".