21840705 has 16 divisors (see below), whose sum is σ = 38828160. Its totient is φ = 11648304.

The previous prime is 21840691. The next prime is 21840743. The reversal of 21840705 is 50704812.

It is not a de Polignac number, because 21840705 - 2⁵ = 21840673 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 80757 + ... + 81026.

It is an arithmetic number, because the mean of its divisors is an integer number (2426760).

Almost surely, 2^21840705 is an apocalyptic number.

It is an amenable number.

21840705 is a deficient number, since it is larger than the sum of its proper divisors (16987455).

21840705 is a wasteful number, since it uses less digits than its factorization.

21840705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161797 (or 161791 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21840705 is about 4673.4040056473. The cubic root of 21840705 is about 279.5260050283.

The spelling of 21840705 in words is "twenty-one million, eight hundred forty thousand, seven hundred five".