21263309 has 2 divisors, whose sum is σ = 21263310. Its totient is φ = 21263308.

The previous prime is 21263279. The next prime is 21263353. The reversal of 21263309 is 90336212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19386409 + 1876900 = 4403^2 + 1370^2 .

It is a cyclic number.

It is not a de Polignac number, because 21263309 - 2¹⁶ = 21197773 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 (21263369) 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, 10631654 + 10631655.

It is an arithmetic number, because the mean of its divisors is an integer number (10631655).

Almost surely, 2^21263309 is an apocalyptic number.

It is an amenable number.

21263309 is a deficient number, since it is larger than the sum of its proper divisors (1).

21263309 is an equidigital number, since it uses as much as digits as its factorization.

21263309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 26.

The square root of 21263309 is about 4611.2155664206. The cubic root of 21263309 is about 277.0407261123.

The spelling of 21263309 in words is "twenty-one million, two hundred sixty-three thousand, three hundred nine".