1991212873 has 16 divisors (see below), whose sum is σ = 2283691536. Its totient is φ = 1719889920.

The previous prime is 1991212859. The next prime is 1991212891. The reversal of 1991212873 is 3782121991.

It can be written as a sum of positive squares in 8 ways, for example, as 4549689 + 1986663184 = 2133^2 + 44572^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991212873 - 2⁵ = 1991212841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991252873) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12193 + ... + 64273.

It is an arithmetic number, because the mean of its divisors is an integer number (142730721).

Almost surely, 2^1991212873 is an apocalyptic number.

1991212873 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1991212873 is a deficient number, since it is larger than the sum of its proper divisors (292478663).

1991212873 is a wasteful number, since it uses less digits than its factorization.

1991212873 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52284.

The product of its digits is 54432, while the sum is 43.

The square root of 1991212873 is about 44623.0083365073. The cubic root of 1991212873 is about 1258.0731599269.

The spelling of 1991212873 in words is "one billion, nine hundred ninety-one million, two hundred twelve thousand, eight hundred seventy-three".