1161991 has 2 divisors, whose sum is σ = 1161992. Its totient is φ = 1161990.

The previous prime is 1161949. The next prime is 1161997. The reversal of 1161991 is 1991611.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1161991 - 2¹³ = 1153799 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1161997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 580995 + 580996.

It is an arithmetic number, because the mean of its divisors is an integer number (580996).

2^1161991 is an apocalyptic number.

1161991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1161991 is an equidigital number, since it uses as much as digits as its factorization.

1161991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 486, while the sum is 28.

The square root of 1161991 is about 1077.9568637010. The cubic root of 1161991 is about 105.1318374198.

The spelling of 1161991 in words is "one million, one hundred sixty-one thousand, nine hundred ninety-one".