21040223 has 4 divisors (see below), whose sum is σ = 21276720. Its totient is φ = 20803728.

The previous prime is 21040213. The next prime is 21040231. The reversal of 21040223 is 32204012.

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 21040223 - 2¹⁶ = 20974687 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21040198 and 21040207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040213) 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, 118115 + ... + 118292.

It is an arithmetic number, because the mean of its divisors is an integer number (5319180).

Almost surely, 2^21040223 is an apocalyptic number.

21040223 is a deficient number, since it is larger than the sum of its proper divisors (236497).

21040223 is an equidigital number, since it uses as much as digits as its factorization.

21040223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 236496.

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21040223 is about 4586.9622845626. The cubic root of 21040223 is about 276.0684516557.

Adding to 21040223 its reverse (32204012), we get a palindrome (53244235).

The spelling of 21040223 in words is "twenty-one million, forty thousand, two hundred twenty-three".