1991991101 has 2 divisors, whose sum is σ = 1991991102. Its totient is φ = 1991991100.

The previous prime is 1991991091. The next prime is 1991991151. The reversal of 1991991101 is 1011991991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1991479876 + 511225 = 44626^2 + 715^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991991101 - 2²⁶ = 1924882237 is a prime.

It is a super-3 number, since 3×1991991101³ (a number of 29 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991991151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995995550 + 995995551.

It is an arithmetic number, because the mean of its divisors is an integer number (995995551).

Almost surely, 2^1991991101 is an apocalyptic number.

It is an amenable number.

1991991101 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991991101 is an equidigital number, since it uses as much as digits as its factorization.

1991991101 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6561, while the sum is 41.

The square root of 1991991101 is about 44631.7275153001. The cubic root of 1991991101 is about 1258.2370366358.

The spelling of 1991991101 in words is "one billion, nine hundred ninety-one million, nine hundred ninety-one thousand, one hundred one".