21816443 has 16 divisors (see below), whose sum is σ = 25318656. Its totient is φ = 18601440.

The previous prime is 21816407. The next prime is 21816451. The reversal of 21816443 is 34461812.

It is not a de Polignac number, because 21816443 - 2¹⁰ = 21815419 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21816463) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12596 + ... + 14222.

It is an arithmetic number, because the mean of its divisors is an integer number (1582416).

Almost surely, 2^21816443 is an apocalyptic number.

21816443 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21816443 is a deficient number, since it is larger than the sum of its proper divisors (3502213).

21816443 is a wasteful number, since it uses less digits than its factorization.

21816443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1714.

The product of its digits is 4608, while the sum is 29.

The square root of 21816443 is about 4670.8075318942. The cubic root of 21816443 is about 279.4224617785.

It can be divided in two parts, 218 and 16443, that added together give a palindrome (16661).

The spelling of 21816443 in words is "twenty-one million, eight hundred sixteen thousand, four hundred forty-three".