21536321 has 2 divisors, whose sum is σ = 21536322. Its totient is φ = 21536320.

The previous prime is 21536287. The next prime is 21536323. The reversal of 21536321 is 12363512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11296321 + 10240000 = 3361^2 + 3200^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21536321 is a prime.

Together with 21536323, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21536323) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768160 + 10768161.

It is an arithmetic number, because the mean of its divisors is an integer number (10768161).

Almost surely, 2^21536321 is an apocalyptic number.

It is an amenable number.

21536321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21536321 is an equidigital number, since it uses as much as digits as its factorization.

21536321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1080, while the sum is 23.

The square root of 21536321 is about 4640.7241891757. The cubic root of 21536321 is about 278.2213830996.

Adding to 21536321 its reverse (12363512), we get a palindrome (33899833).

The spelling of 21536321 in words is "twenty-one million, five hundred thirty-six thousand, three hundred twenty-one".