21286709 has 2 divisors, whose sum is σ = 21286710. Its totient is φ = 21286708.

The previous prime is 21286693. The next prime is 21286717. The reversal of 21286709 is 90768212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16834609 + 4452100 = 4103^2 + 2110^2 .

It is a cyclic number.

It is not a de Polignac number, because 21286709 - 2⁴ = 21286693 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 (21286789) 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, 10643354 + 10643355.

It is an arithmetic number, because the mean of its divisors is an integer number (10643355).

Almost surely, 2^21286709 is an apocalyptic number.

It is an amenable number.

21286709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21286709 is an equidigital number, since it uses as much as digits as its factorization.

21286709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21286709 is about 4613.7521606606. The cubic root of 21286709 is about 277.1423154492.

The spelling of 21286709 in words is "twenty-one million, two hundred eighty-six thousand, seven hundred nine".