21218353 has 16 divisors (see below), whose sum is σ = 24242176. Its totient is φ = 18429120.

The previous prime is 21218333. The next prime is 21218359. The reversal of 21218353 is 35381212.

It is a cyclic number.

It is not a de Polignac number, because 21218353 - 2⁵ = 21218321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21218359) 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, 14200 + ... + 15622.

It is an arithmetic number, because the mean of its divisors is an integer number (1515136).

Almost surely, 2^21218353 is an apocalyptic number.

It is an amenable number.

21218353 is a deficient number, since it is larger than the sum of its proper divisors (3023823).

21218353 is a wasteful number, since it uses less digits than its factorization.

21218353 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1504.

The product of its digits is 1440, while the sum is 25.

The square root of 21218353 is about 4606.3383505774. The cubic root of 21218353 is about 276.8453436874.

Adding to 21218353 its reverse (35381212), we get a palindrome (56599565).

The spelling of 21218353 in words is "twenty-one million, two hundred eighteen thousand, three hundred fifty-three".