91990991991 has 8 divisors (see below), whose sum is σ = 129869635824. Its totient is φ = 57719838080.

The previous prime is 91990991987. The next prime is 91990991993. The reversal of 91990991991 is 19919909919.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 91990991991 - 2² = 91990991987 is a prime.

It is a super-2 number, since 2×91990991991² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91990991993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 901872420 + ... + 901872521.

It is an arithmetic number, because the mean of its divisors is an integer number (16233704478).

Almost surely, 2^91990991991 is an apocalyptic number.

91990991991 is a deficient number, since it is larger than the sum of its proper divisors (37878643833).

91990991991 is a wasteful number, since it uses less digits than its factorization.

91990991991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1803744961.

The product of its (nonzero) digits is 4782969, while the sum is 66.

The spelling of 91990991991 in words is "ninety-one billion, nine hundred ninety million, nine hundred ninety-one thousand, nine hundred ninety-one".