638242138 has 8 divisors (see below), whose sum is σ = 957594132. Its totient is φ = 319044096.

The previous prime is 638242133. The next prime is 638242141. The reversal of 638242138 is 831242836.

It can be written as a sum of positive squares in 2 ways, for example, as 596678329 + 41563809 = 24427^2 + 6447^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×638242138² = 814706053437622088, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 638242097 and 638242106.

It is not an unprimeable number, because it can be changed into a prime (638242133) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27495 + ... + 45082.

Almost surely, 2^638242138 is an apocalyptic number.

638242138 is a deficient number, since it is larger than the sum of its proper divisors (319351994).

638242138 is a wasteful number, since it uses less digits than its factorization.

638242138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76976.

The product of its digits is 55296, while the sum is 37.

The square root of 638242138 is about 25263.4545935428. The cubic root of 638242138 is about 860.9841527720.

The spelling of 638242138 in words is "six hundred thirty-eight million, two hundred forty-two thousand, one hundred thirty-eight".