21984705 has 24 divisors (see below), whose sum is σ = 38736360. Its totient is φ = 11531520.

The previous prime is 21984701. The next prime is 21984713. The reversal of 21984705 is 50748912.

It can be written as a sum of positive squares in 4 ways, for example, as 194481 + 21790224 = 441^2 + 4668^2 .

It is not a de Polignac number, because 21984705 - 2² = 21984701 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21984705.

It is not an unprimeable number, because it can be changed into a prime (21984701) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1260 + ... + 6749.

It is an arithmetic number, because the mean of its divisors is an integer number (1614015).

Almost surely, 2^21984705 is an apocalyptic number.

It is an amenable number.

21984705 is a deficient number, since it is larger than the sum of its proper divisors (16751655).

21984705 is a wasteful number, since it uses less digits than its factorization.

21984705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8081 (or 8078 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21984705 is about 4688.7850238628. The cubic root of 21984705 is about 280.1389828728.

It can be divided in two parts, 2198 and 4705, that added together give a triangular number (6903 = T₁₁₇).

The spelling of 21984705 in words is "twenty-one million, nine hundred eighty-four thousand, seven hundred five".