991201211001 has 8 divisors (see below), whose sum is σ = 1468446238560. Its totient is φ = 660800807316.

The previous prime is 991201210969. The next prime is 991201211017. The reversal of 991201211001 is 100112102199.

It is not a de Polignac number, because 991201211001 - 2⁵ = 991201210969 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 36711155963 = 991201211001 / (9 + 9 + 1 + 2 + 0 + 1 + 2 + 1 + 1 + 0 + 0 + 1).

It is not an unprimeable number, because it can be changed into a prime (991201211101) 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 in 7 ways as a sum of consecutive naturals, for example, 18355577955 + ... + 18355578008.

It is an arithmetic number, because the mean of its divisors is an integer number (183555779820).

Almost surely, 2^991201211001 is an apocalyptic number.

It is an amenable number.

991201211001 is a deficient number, since it is larger than the sum of its proper divisors (477245027559).

991201211001 is a wasteful number, since it uses less digits than its factorization.

991201211001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36711155972 (or 36711155966 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 27.

The spelling of 991201211001 in words is "nine hundred ninety-one billion, two hundred one million, two hundred eleven thousand, one".