21312267 has 4 divisors (see below), whose sum is σ = 28416360. Its totient is φ = 14208176.

The previous prime is 21312257. The next prime is 21312289. The reversal of 21312267 is 76221312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21312267 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21312257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3552042 + ... + 3552047.

It is an arithmetic number, because the mean of its divisors is an integer number (7104090).

Almost surely, 2^21312267 is an apocalyptic number.

21312267 is a deficient number, since it is larger than the sum of its proper divisors (7104093).

21312267 is an equidigital number, since it uses as much as digits as its factorization.

21312267 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7104092.

The product of its digits is 1008, while the sum is 24.

The square root of 21312267 is about 4616.5210927710. The cubic root of 21312267 is about 277.2531885510.

Adding to 21312267 its reverse (76221312), we get a palindrome (97533579).

The spelling of 21312267 in words is "twenty-one million, three hundred twelve thousand, two hundred sixty-seven".