1638555668 has 12 divisors (see below), whose sum is σ = 3018392160. Its totient is φ = 776157912.

The previous prime is 1638555661. The next prime is 1638555683. The reversal of 1638555668 is 8665558361.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638555661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10779896 + ... + 10780047.

It is an arithmetic number, because the mean of its divisors is an integer number (251532680).

Almost surely, 2^1638555668 is an apocalyptic number.

It is an amenable number.

1638555668 is a deficient number, since it is larger than the sum of its proper divisors (1379836492).

1638555668 is a wasteful number, since it uses less digits than its factorization.

1638555668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21559966 (or 21559964 counting only the distinct ones).

The product of its digits is 5184000, while the sum is 53.

The square root of 1638555668 is about 40479.0769163527. The cubic root of 1638555668 is about 1178.9274146986.

The spelling of 1638555668 in words is "one billion, six hundred thirty-eight million, five hundred fifty-five thousand, six hundred sixty-eight".