21367309 has 2 divisors, whose sum is σ = 21367310. Its totient is φ = 21367308.

The previous prime is 21367289. The next prime is 21367331. The reversal of 21367309 is 90376312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21068100 + 299209 = 4590^2 + 547^2 .

It is a cyclic number.

It is not a de Polignac number, because 21367309 - 2¹⁹ = 20843021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21367009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10683654 + 10683655.

It is an arithmetic number, because the mean of its divisors is an integer number (10683655).

Almost surely, 2^21367309 is an apocalyptic number.

It is an amenable number.

21367309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21367309 is an equidigital number, since it uses as much as digits as its factorization.

21367309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6804, while the sum is 31.

The square root of 21367309 is about 4622.4786640935. The cubic root of 21367309 is about 277.4916654695.

The spelling of 21367309 in words is "twenty-one million, three hundred sixty-seven thousand, three hundred nine".