21021223 has 4 divisors (see below), whose sum is σ = 21138840. Its totient is φ = 20903608.

The previous prime is 21021181. The next prime is 21021229. The reversal of 21021223 is 32212012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021223 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 (21021229) 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, 58540 + ... + 58897.

It is an arithmetic number, because the mean of its divisors is an integer number (5284710).

Almost surely, 2^21021223 is an apocalyptic number.

21021223 is a deficient number, since it is larger than the sum of its proper divisors (117617).

21021223 is a wasteful number, since it uses less digits than its factorization.

21021223 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117616.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21021223 is about 4584.8907293413. The cubic root of 21021223 is about 275.9853270572.

Adding to 21021223 its reverse (32212012), we get a palindrome (53233235).

The spelling of 21021223 in words is "twenty-one million, twenty-one thousand, two hundred twenty-three".