21082309 has 2 divisors, whose sum is σ = 21082310. Its totient is φ = 21082308.

The previous prime is 21082301. The next prime is 21082319. The reversal of 21082309 is 90328012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16892100 + 4190209 = 4110^2 + 2047^2 .

It is a cyclic number.

It is not a de Polignac number, because 21082309 - 2³ = 21082301 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21082301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10541154 + 10541155.

It is an arithmetic number, because the mean of its divisors is an integer number (10541155).

Almost surely, 2^21082309 is an apocalyptic number.

It is an amenable number.

21082309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21082309 is an equidigital number, since it uses as much as digits as its factorization.

21082309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 21082309 is about 4591.5475604637. The cubic root of 21082309 is about 276.2523989882.

The spelling of 21082309 in words is "twenty-one million, eighty-two thousand, three hundred nine".