21223643 has 4 divisors (see below), whose sum is σ = 24255600. Its totient is φ = 18191688.

The previous prime is 21223637. The next prime is 21223651. The reversal of 21223643 is 34632212.

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 21223643 - 2⁸ = 21223387 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21223603) 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, 1515968 + ... + 1515981.

It is an arithmetic number, because the mean of its divisors is an integer number (6063900).

Almost surely, 2^21223643 is an apocalyptic number.

21223643 is a deficient number, since it is larger than the sum of its proper divisors (3031957).

21223643 is an equidigital number, since it uses as much as digits as its factorization.

21223643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3031956.

The product of its digits is 1728, while the sum is 23.

The square root of 21223643 is about 4606.9125235889. The cubic root of 21223643 is about 276.8683487745.

Adding to 21223643 its reverse (34632212), we get a palindrome (55855855).

The spelling of 21223643 in words is "twenty-one million, two hundred twenty-three thousand, six hundred forty-three".