638699418 has 120 divisors (see below), whose sum is σ = 1763121492. Its totient is φ = 171714816.

The previous prime is 638699407. The next prime is 638699419. The reversal of 638699418 is 814996836.

638699418 is a `hidden beast` number, since 63 + 86 + 99 + 418 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 638219169 + 480249 = 25263^2 + 693^2 .

It is a super-3 number, since 3×638699418³ (a number of 27 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (638699419) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 132580 + ... + 137312.

Almost surely, 2^638699418 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638699418, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (881560746).

638699418 is an abundant number, since it is smaller than the sum of its proper divisors (1124422074).

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

638699418 is a wasteful number, since it uses less digits than its factorization.

638699418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4778 (or 4762 counting only the distinct ones).

The product of its digits is 2239488, while the sum is 54.

The square root of 638699418 is about 25272.5032001185. The cubic root of 638699418 is about 861.1897261849.

The spelling of 638699418 in words is "six hundred thirty-eight million, six hundred ninety-nine thousand, four hundred eighteen".