21321023 has 4 divisors (see below), whose sum is σ = 22248048. Its totient is φ = 20394000.

The previous prime is 21321019. The next prime is 21321031. The reversal of 21321023 is 32012312.

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 21321023 - 2² = 21321019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21320989 and 21321007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321523) 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, 463478 + ... + 463523.

It is an arithmetic number, because the mean of its divisors is an integer number (5562012).

It is a self-describing number.

Almost surely, 2^21321023 is an apocalyptic number.

21321023 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21321023 is a deficient number, since it is larger than the sum of its proper divisors (927025).

21321023 is an equidigital number, since it uses as much as digits as its factorization.

21321023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 927024.

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

The square root of 21321023 is about 4617.4693285392. The cubic root of 21321023 is about 277.2911525482.

Adding to 21321023 its reverse (32012312), we get a palindrome (53333335).

The spelling of 21321023 in words is "twenty-one million, three hundred twenty-one thousand, twenty-three".