21212223 has 4 divisors (see below), whose sum is σ = 28282968. Its totient is φ = 14141480.

The previous prime is 21212197. The next prime is 21212239. The reversal of 21212223 is 32221212.

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 21212223 - 2⁶ = 21212159 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212263) 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, 3535368 + ... + 3535373.

It is an arithmetic number, because the mean of its divisors is an integer number (7070742).

Almost surely, 2^21212223 is an apocalyptic number.

21212223 is a deficient number, since it is larger than the sum of its proper divisors (7070745).

21212223 is an equidigital number, since it uses as much as digits as its factorization.

21212223 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7070744.

The product of its digits is 96, while the sum is 15.

The square root of 21212223 is about 4605.6729150038. The cubic root of 21212223 is about 276.8186808355.

Adding to 21212223 its reverse (32221212), we get a palindrome (53433435).

The spelling of 21212223 in words is "twenty-one million, two hundred twelve thousand, two hundred twenty-three".