21312263 has 4 divisors (see below), whose sum is σ = 24356880. Its totient is φ = 18267648.

The previous prime is 21312257. The next prime is 21312289. The reversal of 21312263 is 36221312.

It is a happy number.

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

It is not a de Polignac number, because 21312263 - 2¹² = 21308167 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 (21312223) 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, 1522298 + ... + 1522311.

It is an arithmetic number, because the mean of its divisors is an integer number (6089220).

Almost surely, 2^21312263 is an apocalyptic number.

21312263 is a deficient number, since it is larger than the sum of its proper divisors (3044617).

21312263 is an equidigital number, since it uses as much as digits as its factorization.

21312263 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3044616.

The product of its digits is 432, while the sum is 20.

The square root of 21312263 is about 4616.5206595444. The cubic root of 21312263 is about 277.2531712055.

Adding to 21312263 its reverse (36221312), we get a palindrome (57533575).

The spelling of 21312263 in words is "twenty-one million, three hundred twelve thousand, two hundred sixty-three".