21805412 has 12 divisors (see below), whose sum is σ = 38192700. Its totient is φ = 10893216.

The previous prime is 21805411. The next prime is 21805417. The reversal of 21805412 is 21450812.

It can be written as a sum of positive squares in 2 ways, for example, as 16859236 + 4946176 = 4106^2 + 2224^2 .

It is not an unprimeable number, because it can be changed into a prime (21805411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6398 + ... + 9194.

It is an arithmetic number, because the mean of its divisors is an integer number (3182725).

Almost surely, 2^21805412 is an apocalyptic number.

It is an amenable number.

21805412 is a deficient number, since it is larger than the sum of its proper divisors (16387288).

21805412 is a wasteful number, since it uses less digits than its factorization.

21805412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4750 (or 4748 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21805412 is about 4669.6265375295. The cubic root of 21805412 is about 279.3753592510.

The spelling of 21805412 in words is "twenty-one million, eight hundred five thousand, four hundred twelve".