21212023 has 4 divisors (see below), whose sum is σ = 24242320. Its totient is φ = 18181728.

The previous prime is 21212017. The next prime is 21212033. The reversal of 21212023 is 32021212.

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-21212023 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21211994 and 21212012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212033) 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, 1515138 + ... + 1515151.

It is an arithmetic number, because the mean of its divisors is an integer number (6060580).

Almost surely, 2^21212023 is an apocalyptic number.

21212023 is a deficient number, since it is larger than the sum of its proper divisors (3030297).

21212023 is an equidigital number, since it uses as much as digits as its factorization.

21212023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3030296.

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

The square root of 21212023 is about 4605.6512025988. The cubic root of 21212023 is about 276.8178108353.

Adding to 21212023 its reverse (32021212), we get a palindrome (53233235).

The spelling of 21212023 in words is "twenty-one million, two hundred twelve thousand, twenty-three".