991021221012221 has 8 divisors (see below), whose sum is σ = 1160219966063424. Its totient is φ = 828728547187680.

The previous prime is 991021221012167. The next prime is 991021221012241. The reversal of 991021221012221 is 122210122120199.

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 991021221012221 - 2²⁶ = 991021153903357 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991021221012241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1726517806355 + ... + 1726517806928.

It is an arithmetic number, because the mean of its divisors is an integer number (145027495757928).

Almost surely, 2^{991021221012221} is an apocalyptic number.

It is an amenable number.

991021221012221 is a deficient number, since it is larger than the sum of its proper divisors (169198745051203).

991021221012221 is a wasteful number, since it uses less digits than its factorization.

991021221012221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3453035613331.

The product of its (nonzero) digits is 5184, while the sum is 35.

The spelling of 991021221012221 in words is "nine hundred ninety-one trillion, twenty-one billion, two hundred twenty-one million, twelve thousand, two hundred twenty-one".