1638861389 has 48 divisors (see below), whose sum is σ = 1969132032. Its totient is φ = 1359072000.

The previous prime is 1638861383. The next prime is 1638861391. The reversal of 1638861389 is 9831688361.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-1638861389 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (53).

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1638861389.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638861383) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 6047324 + ... + 6047594.

It is an arithmetic number, because the mean of its divisors is an integer number (41023584).

Almost surely, 2^1638861389 is an apocalyptic number.

It is an amenable number.

1638861389 is a deficient number, since it is larger than the sum of its proper divisors (330270643).

1638861389 is a wasteful number, since it uses less digits than its factorization.

1638861389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 410 (or 399 counting only the distinct ones).

The product of its digits is 1492992, while the sum is 53.

The square root of 1638861389 is about 40482.8530244596. The cubic root of 1638861389 is about 1179.0007313928. Note that the first 3 decimals are identical.

It can be divided in two parts, 16388 and 61389, that added together give a palindrome (77777).

The spelling of 1638861389 in words is "one billion, six hundred thirty-eight million, eight hundred sixty-one thousand, three hundred eighty-nine".