21318444 has 96 divisors (see below), whose sum is σ = 63920640. Its totient is φ = 6018624.

The previous prime is 21318443. The next prime is 21318449. The reversal of 21318444 is 44481312.

21318444 is a `hidden beast` number, since 213 + 1 + 8 + 444 = 666.

It is a super-2 number, since 2×21318444² = 908952109162272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21318443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 123142 + ... + 123314.

It is an arithmetic number, because the mean of its divisors is an integer number (665840).

Almost surely, 2^21318444 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21318444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31960320).

21318444 is an abundant number, since it is smaller than the sum of its proper divisors (42602196).

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

21318444 is a wasteful number, since it uses less digits than its factorization.

21318444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 356 (or 348 counting only the distinct ones).

The product of its digits is 3072, while the sum is 27.

The square root of 21318444 is about 4617.1900545678. The cubic root of 21318444 is about 277.2799716788.

Adding to 21318444 its reverse (44481312), we get a palindrome (65799756).

The spelling of 21318444 in words is "twenty-one million, three hundred eighteen thousand, four hundred forty-four".