21121002191 has 4 divisors (see below), whose sum is σ = 21124267584. Its totient is φ = 21117736800.

The previous prime is 21121002187. The next prime is 21121002211. The reversal of 21121002191 is 19120012112.

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 21121002191 - 2² = 21121002187 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121002121) 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, 1622975 + ... + 1635936.

It is an arithmetic number, because the mean of its divisors is an integer number (5281066896).

Almost surely, 2^21121002191 is an apocalyptic number.

21121002191 is a deficient number, since it is larger than the sum of its proper divisors (3265393).

21121002191 is an equidigital number, since it uses as much as digits as its factorization.

21121002191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3265392.

The product of its (nonzero) digits is 72, while the sum is 20.

The spelling of 21121002191 in words is "twenty-one billion, one hundred twenty-one million, two thousand, one hundred ninety-one".