21043818 has 24 divisors (see below), whose sum is σ = 45700356. Its totient is φ = 6998400.

The previous prime is 21043817. The next prime is 21043871. The reversal of 21043818 is 81834012.

21043818 is a `hidden beast` number, since 210 + 438 + 18 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 21040569 + 3249 = 4587^2 + 57^2 .

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21043791 and 21043800.

It is not an unprimeable number, because it can be changed into a prime (21043817) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8658 + ... + 10818.

Almost surely, 2^21043818 is an apocalyptic number.

21043818 is an abundant number, since it is smaller than the sum of its proper divisors (24656538).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21043818 is a wasteful number, since it uses less digits than its factorization.

21043818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2710 (or 2707 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 21043818 is about 4587.3541393705. The cubic root of 21043818 is about 276.0841740741.

The spelling of 21043818 in words is "twenty-one million, forty-three thousand, eight hundred eighteen".