21030823 has 4 divisors (see below), whose sum is σ = 22942728. Its totient is φ = 19118920.

The previous prime is 21030797. The next prime is 21030857. The reversal of 21030823 is 32803012.

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 21030823 - 2⁵ = 21030791 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21030823.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21030923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 955936 + ... + 955957.

It is an arithmetic number, because the mean of its divisors is an integer number (5735682).

Almost surely, 2^21030823 is an apocalyptic number.

21030823 is a deficient number, since it is larger than the sum of its proper divisors (1911905).

21030823 is a wasteful number, since it uses less digits than its factorization.

21030823 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1911904.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21030823 is about 4585.9375268313. The cubic root of 21030823 is about 276.0273331118.

Adding to 21030823 its reverse (32803012), we get a palindrome (53833835).

The spelling of 21030823 in words is "twenty-one million, thirty thousand, eight hundred twenty-three".