21423321 has 6 divisors (see below), whose sum is σ = 30944810. Its totient is φ = 14282208.

The previous prime is 21423319. The next prime is 21423343. The reversal of 21423321 is 12332412.

It can be written as a sum of positive squares in only one way, i.e., 12638025 + 8785296 = 3555^2 + 2964^2 .

It is not a de Polignac number, because 21423321 - 2¹ = 21423319 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21423294 and 21423303.

It is not an unprimeable number, because it can be changed into a prime (21423371) 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 5 ways as a sum of consecutive naturals, for example, 1190176 + ... + 1190193.

Almost surely, 2^21423321 is an apocalyptic number.

It is an amenable number.

21423321 is a deficient number, since it is larger than the sum of its proper divisors (9521489).

21423321 is a wasteful number, since it uses less digits than its factorization.

21423321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2380375 (or 2380372 counting only the distinct ones).

The product of its digits is 288, while the sum is 18.

The square root of 21423321 is about 4628.5333530180. The cubic root of 21423321 is about 277.7339249825.

Adding to 21423321 its reverse (12332412), we get a palindrome (33755733).

Subtracting from 21423321 its reverse (12332412), we obtain a palindrome (9090909).

The spelling of 21423321 in words is "twenty-one million, four hundred twenty-three thousand, three hundred twenty-one".