1991055511 has 2 divisors, whose sum is σ = 1991055512. Its totient is φ = 1991055510.

The previous prime is 1991055503. The next prime is 1991055527. The reversal of 1991055511 is 1155501991.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1991055511 - 2³ = 1991055503 is a prime.

It is a super-2 number, since 2×1991055511² = 7928604095766942242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991055541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995527755 + 995527756.

It is an arithmetic number, because the mean of its divisors is an integer number (995527756).

Almost surely, 2^1991055511 is an apocalyptic number.

1991055511 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991055511 is an equidigital number, since it uses as much as digits as its factorization.

1991055511 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10125, while the sum is 37.

The square root of 1991055511 is about 44621.2450633104. The cubic root of 1991055511 is about 1258.0400179616.

The spelling of 1991055511 in words is "one billion, nine hundred ninety-one million, fifty-five thousand, five hundred eleven".