991438404100 has 27 divisors (see below), whose sum is σ = 2151442944021. Its totient is φ = 396571378800.

The previous prime is 991438404083. The next prime is 991438404149. The reversal of 991438404100 is 1404834199.

The square root of 991438404100 is 995710.

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

991438404100 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 356917825476 + 634520578624 = 597426^2 + 796568^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 9907315 + ... + 10006885.

Almost surely, 2^991438404100 is an apocalyptic number.

991438404100 is the 995710-th square number.

It is an amenable number.

991438404100 is an abundant number, since it is smaller than the sum of its proper divisors (1160004539921).

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

991438404100 is an frugal number, since it uses more digits than its factorization.

991438404100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199156 (or 99578 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 43.

The spelling of 991438404100 in words is "nine hundred ninety-one billion, four hundred thirty-eight million, four hundred four thousand, one hundred".