21705683 has 4 divisors (see below), whose sum is σ = 21715008. Its totient is φ = 21696360.

The previous prime is 21705679. The next prime is 21705689. The reversal of 21705683 is 38650712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21705683 - 2² = 21705679 is a prime.

It is a super-2 number, since 2×21705683² = 942273348992978, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21705689) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2078 + ... + 6908.

It is an arithmetic number, because the mean of its divisors is an integer number (5428752).

Almost surely, 2^21705683 is an apocalyptic number.

21705683 is a deficient number, since it is larger than the sum of its proper divisors (9325).

21705683 is an equidigital number, since it uses as much as digits as its factorization.

21705683 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9324.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21705683 is about 4658.9358226960. The cubic root of 21705683 is about 278.9487922188.

The spelling of 21705683 in words is "twenty-one million, seven hundred five thousand, six hundred eighty-three".