21705887 has 8 divisors (see below), whose sum is σ = 24838176. Its totient is φ = 18581472.

The previous prime is 21705883. The next prime is 21705899. The reversal of 21705887 is 78850712.

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

It is not a de Polignac number, because 21705887 - 2² = 21705883 is a prime.

It is a super-2 number, since 2×21705887² = 942291060913538, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21705887.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705883) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6233 + ... + 9069.

It is an arithmetic number, because the mean of its divisors is an integer number (3104772).

Almost surely, 2^21705887 is an apocalyptic number.

21705887 is a deficient number, since it is larger than the sum of its proper divisors (3132289).

21705887 is a wasteful number, since it uses less digits than its factorization.

21705887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3937.

The product of its (nonzero) digits is 31360, while the sum is 38.

The square root of 21705887 is about 4658.9577160562. The cubic root of 21705887 is about 278.9496661125.

The spelling of 21705887 in words is "twenty-one million, seven hundred five thousand, eight hundred eighty-seven".