9901897991 has 2 divisors, whose sum is σ = 9901897992. Its totient is φ = 9901897990.

The previous prime is 9901897981. The next prime is 9901897997. The reversal of 9901897991 is 1997981099.

9901897991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is an emirp because it is prime and its reverse (1997981099) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9901897991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9901897997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4950948995 + 4950948996.

It is an arithmetic number, because the mean of its divisors is an integer number (4950948996).

Almost surely, 2^9901897991 is an apocalyptic number.

9901897991 is a deficient number, since it is larger than the sum of its proper divisors (1).

9901897991 is an equidigital number, since it uses as much as digits as its factorization.

9901897991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3306744, while the sum is 62.

The square root of 9901897991 is about 99508.2810172098. The cubic root of 9901897991 is about 2147.3663798346.

It can be divided in two parts, 990 and 1897991, that added together give a palindrome (1898981).

The spelling of 9901897991 in words is "nine billion, nine hundred one million, eight hundred ninety-seven thousand, nine hundred ninety-one".