21331366 has 12 divisors (see below), whose sum is σ = 37221228. Its totient is φ = 9141972.

The previous prime is 21331363. The next prime is 21331369. The reversal of 21331366 is 66313312.

It is an interprime number because it is at equal distance from previous prime (21331363) and next prime (21331369).

It is a self number, because there is not a number n which added to its sum of digits gives 21331366.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331361) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 108736 + ... + 108931.

It is an arithmetic number, because the mean of its divisors is an integer number (3101769).

Almost surely, 2^21331366 is an apocalyptic number.

21331366 is a deficient number, since it is larger than the sum of its proper divisors (15889862).

21331366 is a wasteful number, since it uses less digits than its factorization.

21331366 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217683 (or 217676 counting only the distinct ones).

The product of its digits is 1944, while the sum is 25.

The square root of 21331366 is about 4618.5891785263. The cubic root of 21331366 is about 277.3359840235.

Adding to 21331366 its reverse (66313312), we get a palindrome (87644678).

The spelling of 21331366 in words is "twenty-one million, three hundred thirty-one thousand, three hundred sixty-six".