21210023 has 4 divisors (see below), whose sum is σ = 22326360. Its totient is φ = 20093688.

The previous prime is 21210011. The next prime is 21210037. The reversal of 21210023 is 32001212.

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 21210023 - 2¹² = 21205927 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21209986 and 21210013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210053) 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, 558140 + ... + 558177.

It is an arithmetic number, because the mean of its divisors is an integer number (5581590).

Almost surely, 2^21210023 is an apocalyptic number.

21210023 is a deficient number, since it is larger than the sum of its proper divisors (1116337).

21210023 is a wasteful number, since it uses less digits than its factorization.

21210023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1116336.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21210023 is about 4605.4340729186. The cubic root of 21210023 is about 276.8091105333.

Adding to 21210023 its reverse (32001212), we get a palindrome (53211235).

The spelling of 21210023 in words is "twenty-one million, two hundred ten thousand, twenty-three".