21131444209 has 2 divisors, whose sum is σ = 21131444210. Its totient is φ = 21131444208.

The previous prime is 21131444197. The next prime is 21131444233. The reversal of 21131444209 is 90244413112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17614598400 + 3516845809 = 132720^2 + 59303^2 .

It is a cyclic number.

It is not a de Polignac number, because 21131444209 - 2²³ = 21123055601 is a prime.

It is not a weakly prime, because it can be changed into another prime (21131474209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565722104 + 10565722105.

It is an arithmetic number, because the mean of its divisors is an integer number (10565722105).

Almost surely, 2^21131444209 is an apocalyptic number.

It is an amenable number.

21131444209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131444209 is an equidigital number, since it uses as much as digits as its factorization.

21131444209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 31.

The spelling of 21131444209 in words is "twenty-one billion, one hundred thirty-one million, four hundred forty-four thousand, two hundred nine".