1991279845 has 16 divisors (see below), whose sum is σ = 2425272192. Its totient is φ = 1569238720.

The previous prime is 1991279839. The next prime is 1991279957. The reversal of 1991279845 is 5489721991.

It is not a de Polignac number, because 1991279845 - 2³ = 1991279837 is a prime.

It is a super-2 number, since 2×1991279845² = 7930390842206448050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 698994 + ... + 701836.

It is an arithmetic number, because the mean of its divisors is an integer number (151579512).

Almost surely, 2^1991279845 is an apocalyptic number.

It is an amenable number.

1991279845 is a deficient number, since it is larger than the sum of its proper divisors (433992347).

1991279845 is a wasteful number, since it uses less digits than its factorization.

1991279845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4892.

The product of its digits is 1632960, while the sum is 55.

The square root of 1991279845 is about 44623.7587502442. The cubic root of 1991279845 is about 1258.0872643508.

The spelling of 1991279845 in words is "one billion, nine hundred ninety-one million, two hundred seventy-nine thousand, eight hundred forty-five".