101011991 has 2 divisors, whose sum is σ = 101011992. Its totient is φ = 101011990.

The previous prime is 101011973. The next prime is 101012029. The reversal of 101011991 is 199110101.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-101011991 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 (101011931) 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, 50505995 + 50505996.

It is an arithmetic number, because the mean of its divisors is an integer number (50505996).

Almost surely, 2^101011991 is an apocalyptic number.

101011991 is a deficient number, since it is larger than the sum of its proper divisors (1).

101011991 is an equidigital number, since it uses as much as digits as its factorization.

101011991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81, while the sum is 23.

The square root of 101011991 is about 10050.4721779626. The cubic root of 101011991 is about 465.7193798204.

The spelling of 101011991 in words is "one hundred one million, eleven thousand, nine hundred ninety-one".