638138340 has 72 divisors (see below), whose sum is σ = 2212217280. Its totient is φ = 145859904.

The previous prime is 638138329. The next prime is 638138341. The reversal of 638138340 is 43831836.

It is a happy number.

638138340 is a `hidden beast` number, since 638 + 13 + 8 + 3 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 638138295 and 638138304.

It is not an unprimeable number, because it can be changed into a prime (638138341) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 251970 + ... + 254489.

It is an arithmetic number, because the mean of its divisors is an integer number (30725240).

Almost surely, 2^638138340 is an apocalyptic number.

638138340 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

638138340 is an abundant number, since it is smaller than the sum of its proper divisors (1574078940).

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

638138340 is a wasteful number, since it uses less digits than its factorization.

638138340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 506481 (or 506476 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 638138340 is about 25261.4001987222. The cubic root of 638138340 is about 860.9374759844.

The spelling of 638138340 in words is "six hundred thirty-eight million, one hundred thirty-eight thousand, three hundred forty".