991221022122211 has 4 divisors (see below), whose sum is σ = 991643357455672. Its totient is φ = 990798686788752.

The previous prime is 991221022122179. The next prime is 991221022122251. The reversal of 991221022122211 is 112221220122199.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991221022122211 - 2⁵ = 991221022122179 is a prime.

It is a super-2 number, since 2×991221022122211² (a number of 31 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991221022122251) 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, 211167663210 + ... + 211167667903.

It is an arithmetic number, because the mean of its divisors is an integer number (247910839363918).

Almost surely, 2^{991221022122211} is an apocalyptic number.

991221022122211 is a deficient number, since it is larger than the sum of its proper divisors (422335333461).

991221022122211 is a wasteful number, since it uses less digits than its factorization.

991221022122211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 422335333460.

The product of its (nonzero) digits is 10368, while the sum is 37.

The spelling of 991221022122211 in words is "nine hundred ninety-one trillion, two hundred twenty-one billion, twenty-two million, one hundred twenty-two thousand, two hundred eleven".