21318445 has 4 divisors (see below), whose sum is σ = 25582140. Its totient is φ = 17054752.

The previous prime is 21318443. The next prime is 21318449. The reversal of 21318445 is 54481312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3493161 + 17825284 = 1869^2 + 4222^2 .

It is a cyclic number.

It is not a de Polignac number, because 21318445 - 2¹ = 21318443 is a prime.

It is a congruent number.

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

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2131840 + ... + 2131849.

It is an arithmetic number, because the mean of its divisors is an integer number (6395535).

Almost surely, 2^21318445 is an apocalyptic number.

It is an amenable number.

21318445 is a deficient number, since it is larger than the sum of its proper divisors (4263695).

21318445 is an equidigital number, since it uses as much as digits as its factorization.

21318445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4263694.

The product of its digits is 3840, while the sum is 28.

The square root of 21318445 is about 4617.1901628588. The cubic root of 21318445 is about 277.2799760143.

Adding to 21318445 its reverse (54481312), we get a palindrome (75799757).

The spelling of 21318445 in words is "twenty-one million, three hundred eighteen thousand, four hundred forty-five".