21705371 has 2 divisors, whose sum is σ = 21705372. Its totient is φ = 21705370.

The previous prime is 21705367. The next prime is 21705373. The reversal of 21705371 is 17350712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21705371 - 2² = 21705367 is a prime.

It is a super-2 number, since 2×21705371² = 942246260495282, which contains 22 as substring.

Together with 21705373, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21705371.

It is not a weakly prime, because it can be changed into another prime (21705373) 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, 10852685 + 10852686.

It is an arithmetic number, because the mean of its divisors is an integer number (10852686).

Almost surely, 2^21705371 is an apocalyptic number.

21705371 is a deficient number, since it is larger than the sum of its proper divisors (1).

21705371 is an equidigital number, since it uses as much as digits as its factorization.

21705371 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1470, while the sum is 26.

The square root of 21705371 is about 4658.9023385343. The cubic root of 21705371 is about 278.9474556650.

The spelling of 21705371 in words is "twenty-one million, seven hundred five thousand, three hundred seventy-one".