21318443 has 2 divisors, whose sum is σ = 21318444. Its totient is φ = 21318442.

The previous prime is 21318439. The next prime is 21318449. The reversal of 21318443 is 34481312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21318443 - 2² = 21318439 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21318449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10659221 + 10659222.

It is an arithmetic number, because the mean of its divisors is an integer number (10659222).

Almost surely, 2^21318443 is an apocalyptic number.

21318443 is a deficient number, since it is larger than the sum of its proper divisors (1).

21318443 is an equidigital number, since it uses as much as digits as its factorization.

21318443 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2304, while the sum is 26.

The square root of 21318443 is about 4617.1899462768. The cubic root of 21318443 is about 277.2799673433.

Adding to 21318443 its reverse (34481312), we get a palindrome (55799755).

The spelling of 21318443 in words is "twenty-one million, three hundred eighteen thousand, four hundred forty-three".