21425243209 has 2 divisors, whose sum is σ = 21425243210. Its totient is φ = 21425243208.

The previous prime is 21425243173. The next prime is 21425243243. The reversal of 21425243209 is 90234252412.

It is an a-pointer prime, because the next prime (21425243243) can be obtained adding 21425243209 to its sum of digits (34).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14932106809 + 6493136400 = 122197^2 + 80580^2 .

It is a cyclic number.

It is not a de Polignac number, because 21425243209 - 2¹⁹ = 21424718921 is a prime.

It is not a weakly prime, because it can be changed into another prime (21425246209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10712621604 + 10712621605.

It is an arithmetic number, because the mean of its divisors is an integer number (10712621605).

Almost surely, 2^21425243209 is an apocalyptic number.

It is an amenable number.

21425243209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21425243209 is an equidigital number, since it uses as much as digits as its factorization.

21425243209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 34.

The spelling of 21425243209 in words is "twenty-one billion, four hundred twenty-five million, two hundred forty-three thousand, two hundred nine".