1011111991 has 2 divisors, whose sum is σ = 1011111992. Its totient is φ = 1011111990.

The previous prime is 1011111979. The next prime is 1011112049. The reversal of 1011111991 is 1991111101.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1011111991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1011111931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 505555995 + 505555996.

It is an arithmetic number, because the mean of its divisors is an integer number (505555996).

Almost surely, 2^1011111991 is an apocalyptic number.

1011111991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1011111991 is an equidigital number, since it uses as much as digits as its factorization.

1011111991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81, while the sum is 25.

The square root of 1011111991 is about 31797.9872161745. The cubic root of 1011111991 is about 1003.6903614794.

The spelling of 1011111991 in words is "one billion, eleven million, one hundred eleven thousand, nine hundred ninety-one".