21285317 has 2 divisors, whose sum is σ = 21285318. Its totient is φ = 21285316.

The previous prime is 21285311. The next prime is 21285331. The reversal of 21285317 is 71358212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21242881 + 42436 = 4609^2 + 206^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21285317 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21285317.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21285311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10642658 + 10642659.

It is an arithmetic number, because the mean of its divisors is an integer number (10642659).

Almost surely, 2^21285317 is an apocalyptic number.

It is an amenable number.

21285317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21285317 is an equidigital number, since it uses as much as digits as its factorization.

21285317 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3360, while the sum is 29.

The square root of 21285317 is about 4613.6013048377. The cubic root of 21285317 is about 277.1362742693.

The spelling of 21285317 in words is "twenty-one million, two hundred eighty-five thousand, three hundred seventeen".