21705319 has 2 divisors, whose sum is σ = 21705320. Its totient is φ = 21705318.

The previous prime is 21705317. The next prime is 21705323. The reversal of 21705319 is 91350712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21705319 - 2¹ = 21705317 is a prime.

It is a super-2 number, since 2×21705319² = 942241745783522, which contains 22 as substring.

Together with 21705317, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21705317) 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, 10852659 + 10852660.

It is an arithmetic number, because the mean of its divisors is an integer number (10852660).

Almost surely, 2^21705319 is an apocalyptic number.

21705319 is a deficient number, since it is larger than the sum of its proper divisors (1).

21705319 is an equidigital number, since it uses as much as digits as its factorization.

21705319 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21705319 is about 4658.8967578172. The cubic root of 21705319 is about 278.9472329048.

The spelling of 21705319 in words is "twenty-one million, seven hundred five thousand, three hundred nineteen".