21607321 has 2 divisors, whose sum is σ = 21607322. Its totient is φ = 21607320.

The previous prime is 21607319. The next prime is 21607361. The reversal of 21607321 is 12370612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17347225 + 4260096 = 4165^2 + 2064^2 .

It is a cyclic number.

It is not a de Polignac number, because 21607321 - 2¹ = 21607319 is a prime.

Together with 21607319, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21607292 and 21607301.

It is not a weakly prime, because it can be changed into another prime (21607301) 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 as a sum of consecutive naturals, namely, 10803660 + 10803661.

It is an arithmetic number, because the mean of its divisors is an integer number (10803661).

Almost surely, 2^21607321 is an apocalyptic number.

It is an amenable number.

21607321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21607321 is an equidigital number, since it uses as much as digits as its factorization.

21607321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21607321 is about 4648.3675629193. The cubic root of 21607321 is about 278.5267904181.

Adding to 21607321 its reverse (12370612), we get a palindrome (33977933).

The spelling of 21607321 in words is "twenty-one million, six hundred seven thousand, three hundred twenty-one".