1911991 has 2 divisors, whose sum is σ = 1911992. Its totient is φ = 1911990.

The previous prime is 1911977. The next prime is 1912019. The reversal of 1911991 is 1991191.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1911991 is a prime.

It is a pancake number, because a pancake can be divided into 1911991 parts by 1955 straight cuts.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1911911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 955995 + 955996.

It is an arithmetic number, because the mean of its divisors is an integer number (955996).

2^1911991 is an apocalyptic number.

1911991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1911991 is an equidigital number, since it uses as much as digits as its factorization.

1911991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 729, while the sum is 31.

The square root of 1911991 is about 1382.7476270094. The cubic root of 1911991 is about 124.1162411542.

The spelling of 1911991 in words is "one million, nine hundred eleven thousand, nine hundred ninety-one".