21708361 has 2 divisors, whose sum is σ = 21708362. Its totient is φ = 21708360.

The previous prime is 21708353. The next prime is 21708367. The reversal of 21708361 is 16380712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18966025 + 2742336 = 4355^2 + 1656^2 .

It is a cyclic number.

It is not a de Polignac number, because 21708361 - 2³ = 21708353 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21708367) 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, 10854180 + 10854181.

It is an arithmetic number, because the mean of its divisors is an integer number (10854181).

Almost surely, 2^21708361 is an apocalyptic number.

It is an amenable number.

21708361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21708361 is an equidigital number, since it uses as much as digits as its factorization.

21708361 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21708361 is about 4659.2232185204. The cubic root of 21708361 is about 278.9602637790.

The spelling of 21708361 in words is "twenty-one million, seven hundred eight thousand, three hundred sixty-one".