21310309 has 2 divisors, whose sum is σ = 21310310. Its totient is φ = 21310308.

The previous prime is 21310301. The next prime is 21310319. The reversal of 21310309 is 90301312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19980900 + 1329409 = 4470^2 + 1153^2 .

It is a cyclic number.

It is not a de Polignac number, because 21310309 - 2³ = 21310301 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21310301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655154 + 10655155.

It is an arithmetic number, because the mean of its divisors is an integer number (10655155).

Almost surely, 2^21310309 is an apocalyptic number.

It is an amenable number.

21310309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21310309 is an equidigital number, since it uses as much as digits as its factorization.

21310309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162, while the sum is 19.

The square root of 21310309 is about 4616.3090234515. The cubic root of 21310309 is about 277.2446976919.

The spelling of 21310309 in words is "twenty-one million, three hundred ten thousand, three hundred nine".