1171991 has 2 divisors, whose sum is σ = 1171992. Its totient is φ = 1171990.

The previous prime is 1171981. The next prime is 1171999. The reversal of 1171991 is 1991711.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1171991 - 2⁶ = 1171927 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1171999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 585995 + 585996.

It is an arithmetic number, because the mean of its divisors is an integer number (585996).

2^1171991 is an apocalyptic number.

1171991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1171991 is an equidigital number, since it uses as much as digits as its factorization.

1171991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 567, while the sum is 29.

The square root of 1171991 is about 1082.5853315097. The cubic root of 1171991 is about 105.4325617391.

The spelling of 1171991 in words is "one million, one hundred seventy-one thousand, nine hundred ninety-one".