21786705 has 32 divisors (see below), whose sum is σ = 39294720. Its totient is φ = 11450880.

The previous prime is 21786701. The next prime is 21786757. The reversal of 21786705 is 50768712.

It is not a de Polignac number, because 21786705 - 2² = 21786701 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21786705.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21786701) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8449 + ... + 10721.

It is an arithmetic number, because the mean of its divisors is an integer number (1227960).

Almost surely, 2^21786705 is an apocalyptic number.

It is an amenable number.

21786705 is a deficient number, since it is larger than the sum of its proper divisors (17508015).

21786705 is a wasteful number, since it uses less digits than its factorization.

21786705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2358 (or 2352 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 21786705 is about 4667.6230567603. The cubic root of 21786705 is about 279.2954437677.

The spelling of 21786705 in words is "twenty-one million, seven hundred eighty-six thousand, seven hundred five".