21804218 has 8 divisors (see below), whose sum is σ = 32727348. Its totient is φ = 10895104.

The previous prime is 21804197. The next prime is 21804227. The reversal of 21804218 is 81240812.

It can be written as a sum of positive squares in 2 ways, for example, as 20857489 + 946729 = 4567^2 + 973^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2330 + ... + 7002.

Almost surely, 2^21804218 is an apocalyptic number.

21804218 is a deficient number, since it is larger than the sum of its proper divisors (10923130).

21804218 is a wasteful number, since it uses less digits than its factorization.

21804218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7008.

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 21804218 is about 4669.4986882962. The cubic root of 21804218 is about 279.3702599012.

It can be divided in two parts, 21804 and 218, that added together give a palindrome (22022).

The spelling of 21804218 in words is "twenty-one million, eight hundred four thousand, two hundred eighteen".