1201011991 has 2 divisors, whose sum is σ = 1201011992. Its totient is φ = 1201011990.

The previous prime is 1201011961. The next prime is 1201012027. The reversal of 1201011991 is 1991101021.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1201011991 - 2⁷ = 1201011863 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1201011901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 600505995 + 600505996.

It is an arithmetic number, because the mean of its divisors is an integer number (600505996).

Almost surely, 2^1201011991 is an apocalyptic number.

1201011991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1201011991 is an equidigital number, since it uses as much as digits as its factorization.

1201011991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 162, while the sum is 25.

The square root of 1201011991 is about 34655.6199050024. The cubic root of 1201011991 is about 1062.9572077229.

The spelling of 1201011991 in words is "one billion, two hundred one million, eleven thousand, nine hundred ninety-one".