21152309 has 2 divisors, whose sum is σ = 21152310. Its totient is φ = 21152308.

The previous prime is 21152291. The next prime is 21152311. The reversal of 21152309 is 90325112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20729809 + 422500 = 4553^2 + 650^2 .

It is a cyclic number.

It is not a de Polignac number, because 21152309 - 2¹² = 21148213 is a prime.

Together with 21152311, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21152399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10576154 + 10576155.

It is an arithmetic number, because the mean of its divisors is an integer number (10576155).

Almost surely, 2^21152309 is an apocalyptic number.

It is an amenable number.

21152309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21152309 is an equidigital number, since it uses as much as digits as its factorization.

21152309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21152309 is about 4599.1639457623. The cubic root of 21152309 is about 276.5578099516.

The spelling of 21152309 in words is "twenty-one million, one hundred fifty-two thousand, three hundred nine".