21202102091 has 4 divisors (see below), whose sum is σ = 21205020552. Its totient is φ = 21199183632.

The previous prime is 21202102073. The next prime is 21202102099. The reversal of 21202102091 is 19020120212.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21202102091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21202102099) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1448306 + ... + 1462871.

It is an arithmetic number, because the mean of its divisors is an integer number (5301255138).

Almost surely, 2^21202102091 is an apocalyptic number.

21202102091 is a deficient number, since it is larger than the sum of its proper divisors (2918461).

21202102091 is an equidigital number, since it uses as much as digits as its factorization.

21202102091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2918460.

The product of its (nonzero) digits is 144, while the sum is 20.

The spelling of 21202102091 in words is "twenty-one billion, two hundred two million, one hundred two thousand, ninety-one".