21312443 has 4 divisors (see below), whose sum is σ = 21508080. Its totient is φ = 21116808.

The previous prime is 21312439. The next prime is 21312449. The reversal of 21312443 is 34421312.

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

It is a cyclic number.

It is not a de Polignac number, because 21312443 - 2² = 21312439 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21312449) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 97655 + ... + 97872.

It is an arithmetic number, because the mean of its divisors is an integer number (5377020).

Almost surely, 2^21312443 is an apocalyptic number.

21312443 is a deficient number, since it is larger than the sum of its proper divisors (195637).

21312443 is a wasteful number, since it uses less digits than its factorization.

21312443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195636.

The product of its digits is 576, while the sum is 20.

The square root of 21312443 is about 4616.5401547046. The cubic root of 21312443 is about 277.2539517488.

Adding to 21312443 its reverse (34421312), we get a palindrome (55733755).

The spelling of 21312443 in words is "twenty-one million, three hundred twelve thousand, four hundred forty-three".