21318133 has 6 divisors (see below), whose sum is σ = 22499574. Its totient is φ = 20195784.

The previous prime is 21318109. The next prime is 21318149. The reversal of 21318133 is 33181312.

It can be written as a sum of positive squares in only one way, i.e., 21316689 + 1444 = 4617^2 + 38^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21318133 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21318533) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 29166 + ... + 29887.

It is an arithmetic number, because the mean of its divisors is an integer number (3749929).

Almost surely, 2^21318133 is an apocalyptic number.

It is an amenable number.

21318133 is a deficient number, since it is larger than the sum of its proper divisors (1181441).

21318133 is an equidigital number, since it uses as much as digits as its factorization.

21318133 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59091 (or 59072 counting only the distinct ones).

The product of its digits is 432, while the sum is 22.

The square root of 21318133 is about 4617.1563759526. The cubic root of 21318133 is about 277.2786233238.

Adding to 21318133 its reverse (33181312), we get a palindrome (54499445).

The spelling of 21318133 in words is "twenty-one million, three hundred eighteen thousand, one hundred thirty-three".