21324321 has 12 divisors (see below), whose sum is σ = 31634772. Its totient is φ = 13831776.

The previous prime is 21324313. The next prime is 21324361. The reversal of 21324321 is 12342312.

21324321 is a `hidden beast` number, since 21 + 324 + 321 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 8643600 + 12680721 = 2940^2 + 3561^2 .

It is not a de Polignac number, because 21324321 - 2³ = 21324313 is a prime.

It is a super-2 number, since 2×21324321² = 909453332222082, which contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21324294 and 21324303.

It is not an unprimeable number, because it can be changed into a prime (21324301) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31686 + ... + 32351.

It is an arithmetic number, because the mean of its divisors is an integer number (2636231).

Almost surely, 2^21324321 is an apocalyptic number.

It is an amenable number.

21324321 is a deficient number, since it is larger than the sum of its proper divisors (10310451).

21324321 is a wasteful number, since it uses less digits than its factorization.

21324321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64080 (or 64077 counting only the distinct ones).

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

The square root of 21324321 is about 4617.8264367557. The cubic root of 21324321 is about 277.3054492210.

Adding to 21324321 its reverse (12342312), we get a palindrome (33666633).

Subtracting from 21324321 its reverse (12342312), we obtain a square (8982009 = 2997²).

The spelling of 21324321 in words is "twenty-one million, three hundred twenty-four thousand, three hundred twenty-one".