21235129309 has 2 divisors, whose sum is σ = 21235129310. Its totient is φ = 21235129308.

The previous prime is 21235129259. The next prime is 21235129319. The reversal of 21235129309 is 90392153212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18689624100 + 2545505209 = 136710^2 + 50453^2 .

It is a cyclic number.

It is not a de Polignac number, because 21235129309 - 2²⁹ = 20698258397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21235129319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617564654 + 10617564655.

It is an arithmetic number, because the mean of its divisors is an integer number (10617564655).

Almost surely, 2^21235129309 is an apocalyptic number.

It is an amenable number.

21235129309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21235129309 is an equidigital number, since it uses as much as digits as its factorization.

21235129309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 29160, while the sum is 37.

It can be divided in two parts, 21235 and 129309, that added together give a square (150544 = 388²).

The spelling of 21235129309 in words is "twenty-one billion, two hundred thirty-five million, one hundred twenty-nine thousand, three hundred nine".