1638638639 has 16 divisors (see below), whose sum is σ = 1808262144. Its totient is φ = 1472512800.

The previous prime is 1638638629. The next prime is 1638638663. The reversal of 1638638639 is 9368368361.

It is not a de Polignac number, because 1638638639 - 2⁴ = 1638638623 is a prime.

It is a super-3 number, since 3×1638638639³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638638629) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 874874 + ... + 876744.

It is an arithmetic number, because the mean of its divisors is an integer number (113016384).

Almost surely, 2^1638638639 is an apocalyptic number.

1638638639 is a deficient number, since it is larger than the sum of its proper divisors (169623505).

1638638639 is a wasteful number, since it uses less digits than its factorization.

1638638639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2758.

The product of its digits is 3359232, while the sum is 53.

The square root of 1638638639 is about 40480.1017661764. The cubic root of 1638638639 is about 1178.9473133483.

The spelling of 1638638639 in words is "one billion, six hundred thirty-eight million, six hundred thirty-eight thousand, six hundred thirty-nine".