21432321 has 12 divisors (see below), whose sum is σ = 31073172. Its totient is φ = 14234976.

The previous prime is 21432317. The next prime is 21432331. The reversal of 21432321 is 12323412.

It can be written as a sum of positive squares in 2 ways, for example, as 9217296 + 12215025 = 3036^2 + 3495^2 .

It is not a de Polignac number, because 21432321 - 2² = 21432317 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21432294 and 21432303.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21432311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1806 + ... + 6791.

It is an arithmetic number, because the mean of its divisors is an integer number (2589431).

Almost surely, 2^21432321 is an apocalyptic number.

It is an amenable number.

21432321 is a deficient number, since it is larger than the sum of its proper divisors (9640851).

21432321 is a wasteful number, since it uses less digits than its factorization.

21432321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8880 (or 8877 counting only the distinct ones).

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

The square root of 21432321 is about 4629.5054811502. The cubic root of 21432321 is about 277.7728118164.

Adding to 21432321 its reverse (12323412), we get a palindrome (33755733).

The spelling of 21432321 in words is "twenty-one million, four hundred thirty-two thousand, three hundred twenty-one".