21012443 has 4 divisors (see below), whose sum is σ = 21737040. Its totient is φ = 20287848.

The previous prime is 21012421. The next prime is 21012449. The reversal of 21012443 is 34421012.

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 21012443 - 2¹² = 21008347 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21012449) 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, 362255 + ... + 362312.

It is an arithmetic number, because the mean of its divisors is an integer number (5434260).

Almost surely, 2^21012443 is an apocalyptic number.

21012443 is a deficient number, since it is larger than the sum of its proper divisors (724597).

21012443 is an equidigital number, since it uses as much as digits as its factorization.

21012443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724596.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21012443 is about 4583.9331365106. The cubic root of 21012443 is about 275.9468978214.

Adding to 21012443 its reverse (34421012), we get a palindrome (55433455).

The spelling of 21012443 in words is "twenty-one million, twelve thousand, four hundred forty-three".