21765713 has 2 divisors, whose sum is σ = 21765714. Its totient is φ = 21765712.

The previous prime is 21765703. The next prime is 21765719. The reversal of 21765713 is 31756712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21641104 + 124609 = 4652^2 + 353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21765713 - 2¹² = 21761617 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21765713.

It is not a weakly prime, because it can be changed into another prime (21765719) 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, 10882856 + 10882857.

It is an arithmetic number, because the mean of its divisors is an integer number (10882857).

Almost surely, 2^21765713 is an apocalyptic number.

It is an amenable number.

21765713 is a deficient number, since it is larger than the sum of its proper divisors (1).

21765713 is an equidigital number, since it uses as much as digits as its factorization.

21765713 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8820, while the sum is 32.

The square root of 21765713 is about 4665.3738328241. The cubic root of 21765713 is about 279.2057123773.

Subtracting 21765713 from its reverse (31756712), we obtain a palindrome (9990999).

The spelling of 21765713 in words is "twenty-one million, seven hundred sixty-five thousand, seven hundred thirteen".