21001223 has 4 divisors (see below), whose sum is σ = 21021048. Its totient is φ = 20981400.

The previous prime is 21001187. The next prime is 21001247. The reversal of 21001223 is 32210012.

It is a happy number.

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 21001223 - 2¹⁴ = 20984839 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 (21001523) 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, 8228 + ... + 10473.

It is an arithmetic number, because the mean of its divisors is an integer number (5255262).

Almost surely, 2^21001223 is an apocalyptic number.

21001223 is a deficient number, since it is larger than the sum of its proper divisors (19825).

21001223 is a wasteful number, since it uses less digits than its factorization.

21001223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19824.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21001223 is about 4582.7091332529. The cubic root of 21001223 is about 275.8977733504.

Adding to 21001223 its reverse (32210012), we get a palindrome (53211235).

The spelling of 21001223 in words is "twenty-one million, one thousand, two hundred twenty-three".