21985305 has 16 divisors (see below), whose sum is σ = 35623680. Its totient is φ = 11576448.

The previous prime is 21985303. The next prime is 21985319. The reversal of 21985305 is 50358912.

It is not a de Polignac number, because 21985305 - 2¹ = 21985303 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21985303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8092 + ... + 10461.

It is an arithmetic number, because the mean of its divisors is an integer number (2226480).

Almost surely, 2^21985305 is an apocalyptic number.

It is an amenable number.

21985305 is a deficient number, since it is larger than the sum of its proper divisors (13638375).

21985305 is a wasteful number, since it uses less digits than its factorization.

21985305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18640.

The product of its (nonzero) digits is 10800, while the sum is 33.

The square root of 21985305 is about 4688.8490058862. The cubic root of 21985305 is about 280.1415313394.

It can be divided in two parts, 2198 and 5305, that added together give a triangular number (7503 = T₁₂₂).

The spelling of 21985305 in words is "twenty-one million, nine hundred eighty-five thousand, three hundred five".