1638668988 has 96 divisors (see below), whose sum is σ = 4650750720. Its totient is φ = 494838720.

The previous prime is 1638668957. The next prime is 1638668989. The reversal of 1638668988 is 8898668361.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1638668989) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 362470 + ... + 366962.

It is an arithmetic number, because the mean of its divisors is an integer number (48445320).

Almost surely, 2^1638668988 is an apocalyptic number.

1638668988 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1638668988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2325375360).

1638668988 is an abundant number, since it is smaller than the sum of its proper divisors (3012081732).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1638668988 is a wasteful number, since it uses less digits than its factorization.

1638668988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4824 (or 4816 counting only the distinct ones).

The product of its digits is 23887872, while the sum is 63.

The square root of 1638668988 is about 40480.4766276288. The cubic root of 1638668988 is about 1178.9545916768.

The spelling of 1638668988 in words is "one billion, six hundred thirty-eight million, six hundred sixty-eight thousand, nine hundred eighty-eight".