1638967138 has 4 divisors (see below), whose sum is σ = 2458450710. Its totient is φ = 819483568.

The previous prime is 1638967123. The next prime is 1638967147. The reversal of 1638967138 is 8317698361.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 1595762809 + 43204329 = 39947^2 + 6573^2 .

It is a super-2 number, since 2×1638967138² = 5372426558887822088, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409741783 + ... + 409741786.

Almost surely, 2^1638967138 is an apocalyptic number.

1638967138 is a deficient number, since it is larger than the sum of its proper divisors (819483572).

1638967138 is an equidigital number, since it uses as much as digits as its factorization.

1638967138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 819483571.

The product of its digits is 1306368, while the sum is 52.

The square root of 1638967138 is about 40484.1590995787. The cubic root of 1638967138 is about 1179.0260895404.

The spelling of 1638967138 in words is "one billion, six hundred thirty-eight million, nine hundred sixty-seven thousand, one hundred thirty-eight".