21275909 has 2 divisors, whose sum is σ = 21275910. Its totient is φ = 21275908.

The previous prime is 21275893. The next prime is 21275941. The reversal of 21275909 is 90957212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15288100 + 5987809 = 3910^2 + 2447^2 .

It is a cyclic number.

It is not a de Polignac number, because 21275909 - 2⁴ = 21275893 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21275209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10637954 + 10637955.

It is an arithmetic number, because the mean of its divisors is an integer number (10637955).

Almost surely, 2^21275909 is an apocalyptic number.

It is an amenable number.

21275909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21275909 is an equidigital number, since it uses as much as digits as its factorization.

21275909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11340, while the sum is 35.

The square root of 21275909 is about 4612.5815981942. The cubic root of 21275909 is about 277.0954373190.

The spelling of 21275909 in words is "twenty-one million, two hundred seventy-five thousand, nine hundred nine".