21383309 has 2 divisors, whose sum is σ = 21383310. Its totient is φ = 21383308.

The previous prime is 21383291. The next prime is 21383317. The reversal of 21383309 is 90338312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19272100 + 2111209 = 4390^2 + 1453^2 .

It is a cyclic number.

It is not a de Polignac number, because 21383309 - 2⁸ = 21383053 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21383389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10691654 + 10691655.

It is an arithmetic number, because the mean of its divisors is an integer number (10691655).

Almost surely, 2^21383309 is an apocalyptic number.

It is an amenable number.

21383309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21383309 is an equidigital number, since it uses as much as digits as its factorization.

21383309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3888, while the sum is 29.

The square root of 21383309 is about 4624.2090134422. The cubic root of 21383309 is about 277.5609107966.

The spelling of 21383309 in words is "twenty-one million, three hundred eighty-three thousand, three hundred nine".