21021223109 has 4 divisors (see below), whose sum is σ = 21021571500. Its totient is φ = 21020874720.

The previous prime is 21021223087. The next prime is 21021223123. The reversal of 21021223109 is 90132212012.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1979983009 + 19041240100 = 44497^2 + 137990^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021223109 - 2²⁰ = 21020174533 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 (21021223409) 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, 57734 + ... + 213015.

It is an arithmetic number, because the mean of its divisors is an integer number (5255392875).

Almost surely, 2^21021223109 is an apocalyptic number.

It is an amenable number.

21021223109 is a deficient number, since it is larger than the sum of its proper divisors (348391).

21021223109 is an equidigital number, since it uses as much as digits as its factorization.

21021223109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 348390.

The product of its (nonzero) digits is 432, while the sum is 23.

The spelling of 21021223109 in words is "twenty-one billion, twenty-one million, two hundred twenty-three thousand, one hundred nine".