991001012211121 has 4 divisors (see below), whose sum is σ = 991001281590000. Its totient is φ = 991000742832244.

The previous prime is 991001012211083. The next prime is 991001012211193. The reversal of 991001012211121 is 121112210100199.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 991001012211121 - 2¹⁷ = 991001012080049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991001012214121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 129093691 + ... + 136554688.

It is an arithmetic number, because the mean of its divisors is an integer number (247750320397500).

Almost surely, 2^{991001012211121} is an apocalyptic number.

It is an amenable number.

991001012211121 is a deficient number, since it is larger than the sum of its proper divisors (269378879).

991001012211121 is a wasteful number, since it uses less digits than its factorization.

991001012211121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269378878.

The product of its (nonzero) digits is 648, while the sum is 31.

The spelling of 991001012211121 in words is "nine hundred ninety-one trillion, one billion, twelve million, two hundred eleven thousand, one hundred twenty-one".