21308309 has 8 divisors (see below), whose sum is σ = 23280480. Its totient is φ = 19342000.

The previous prime is 21308303. The next prime is 21308311. The reversal of 21308309 is 90380312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21308309 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10259 + ... + 12159.

It is an arithmetic number, because the mean of its divisors is an integer number (2910060).

Almost surely, 2^21308309 is an apocalyptic number.

It is an amenable number.

21308309 is a deficient number, since it is larger than the sum of its proper divisors (1972171).

21308309 is a wasteful number, since it uses less digits than its factorization.

21308309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2931.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 21308309 is about 4616.0923950892. The cubic root of 21308309 is about 277.2360241630.

The spelling of 21308309 in words is "twenty-one million, three hundred eight thousand, three hundred nine".