1638220804900 has 81 divisors (see below), whose sum is σ = 3776855682649. Its totient is φ = 616660034560.

The previous prime is 1638220804867. The next prime is 1638220804901. The reversal of 1638220804900 is 94080228361.

The square root of 1638220804900 is 1279930.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 850685250276 + 787535554624 = 922326^2 + 887432^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1638220804901) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 217584336 + ... + 217591864.

Almost surely, 2^{1638220804900} is an apocalyptic number.

1638220804900 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1638220804900 is the 1279930-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1638220804900

1638220804900 is an abundant number, since it is smaller than the sum of its proper divisors (2138634877749).

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

1638220804900 is an frugal number, since it uses more digits than its factorization.

1638220804900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15106 (or 7553 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 43.

The spelling of 1638220804900 in words is "one trillion, six hundred thirty-eight billion, two hundred twenty million, eight hundred four thousand, nine hundred".