21705806 has 8 divisors (see below), whose sum is σ = 32863320. Its totient is φ = 10751368.

The previous prime is 21705793. The next prime is 21705829. The reversal of 21705806 is 60850712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21705806² = 942284028219272, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50501 + ... + 50928.

It is an arithmetic number, because the mean of its divisors is an integer number (4107915).

Almost surely, 2^21705806 is an apocalyptic number.

21705806 is a deficient number, since it is larger than the sum of its proper divisors (11157514).

21705806 is a wasteful number, since it uses less digits than its factorization.

21705806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101538.

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 21705806 is about 4658.9490231167. The cubic root of 21705806 is about 278.9493191260.

The spelling of 21705806 in words is "twenty-one million, seven hundred five thousand, eight hundred six".