21716729 has 2 divisors, whose sum is σ = 21716730. Its totient is φ = 21716728.

The previous prime is 21716713. The next prime is 21716731. The reversal of 21716729 is 92761712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21641104 + 75625 = 4652^2 + 275^2 .

It is a cyclic number.

It is not a de Polignac number, because 21716729 - 2⁴ = 21716713 is a prime.

Together with 21716731, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21716749) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858364 + 10858365.

It is an arithmetic number, because the mean of its divisors is an integer number (10858365).

Almost surely, 2^21716729 is an apocalyptic number.

It is an amenable number.

21716729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21716729 is an equidigital number, since it uses as much as digits as its factorization.

21716729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10584, while the sum is 35.

The square root of 21716729 is about 4660.1211357646. The cubic root of 21716729 is about 278.9961031131.

The spelling of 21716729 in words is "twenty-one million, seven hundred sixteen thousand, seven hundred twenty-nine".