21032309 has 2 divisors, whose sum is σ = 21032310. Its totient is φ = 21032308.

The previous prime is 21032299. The next prime is 21032329. The reversal of 21032309 is 90323012.

It is an a-pointer prime, because the next prime (21032329) can be obtained adding 21032309 to its sum of digits (20).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20729809 + 302500 = 4553^2 + 550^2 .

It is a cyclic number.

It is not a de Polignac number, because 21032309 - 2⁴ = 21032293 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21032329) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10516154 + 10516155.

It is an arithmetic number, because the mean of its divisors is an integer number (10516155).

Almost surely, 2^21032309 is an apocalyptic number.

It is an amenable number.

21032309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21032309 is an equidigital number, since it uses as much as digits as its factorization.

21032309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 20.

The square root of 21032309 is about 4586.0995410043. The cubic root of 21032309 is about 276.0338341565.

The spelling of 21032309 in words is "twenty-one million, thirty-two thousand, three hundred nine".