21684713 has 2 divisors, whose sum is σ = 21684714. Its totient is φ = 21684712.

The previous prime is 21684679. The next prime is 21684739. The reversal of 21684713 is 31748612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20403289 + 1281424 = 4517^2 + 1132^2 .

It is a cyclic number.

It is not a de Polignac number, because 21684713 - 2²⁰ = 20636137 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21684713.

It is not a weakly prime, because it can be changed into another prime (21684763) 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, 10842356 + 10842357.

It is an arithmetic number, because the mean of its divisors is an integer number (10842357).

Almost surely, 2^21684713 is an apocalyptic number.

It is an amenable number.

21684713 is a deficient number, since it is larger than the sum of its proper divisors (1).

21684713 is an equidigital number, since it uses as much as digits as its factorization.

21684713 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8064, while the sum is 32.

The square root of 21684713 is about 4656.6847649374. The cubic root of 21684713 is about 278.8589318668.

The spelling of 21684713 in words is "twenty-one million, six hundred eighty-four thousand, seven hundred thirteen".