21218323 has 8 divisors (see below), whose sum is σ = 24744800. Its totient is φ = 18186840.

The previous prime is 21218321. The next prime is 21218333. The reversal of 21218323 is 32381212.

It is not a de Polignac number, because 21218323 - 2¹ = 21218321 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21218294 and 21218303.

It is not an unprimeable number, because it can be changed into a prime (21218321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30588 + ... + 31273.

It is an arithmetic number, because the mean of its divisors is an integer number (3093100).

Almost surely, 2^21218323 is an apocalyptic number.

21218323 is a deficient number, since it is larger than the sum of its proper divisors (3526477).

21218323 is an frugal number, since it uses more digits than its factorization.

21218323 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61882 (or 61868 counting only the distinct ones).

The product of its digits is 576, while the sum is 22.

The square root of 21218323 is about 4606.3350941936. The cubic root of 21218323 is about 276.8452132128.

Adding to 21218323 its reverse (32381212), we get a palindrome (53599535).

The spelling of 21218323 in words is "twenty-one million, two hundred eighteen thousand, three hundred twenty-three".