21213023 has 4 divisors (see below), whose sum is σ = 22844808. Its totient is φ = 19581240.

The previous prime is 21213013. The next prime is 21213029. The reversal of 21213023 is 32031212.

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 21213023 - 2¹² = 21208927 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21212989 and 21213007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213029) 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, 815873 + ... + 815898.

It is an arithmetic number, because the mean of its divisors is an integer number (5711202).

Almost surely, 2^21213023 is an apocalyptic number.

21213023 is a deficient number, since it is larger than the sum of its proper divisors (1631785).

21213023 is a wasteful number, since it uses less digits than its factorization.

21213023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1631784.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21213023 is about 4605.7597636004. The cubic root of 21213023 is about 276.8221607813.

Adding to 21213023 its reverse (32031212), we get a palindrome (53244235).

The spelling of 21213023 in words is "twenty-one million, two hundred thirteen thousand, twenty-three".