21353281 has 2 divisors, whose sum is σ = 21353282. Its totient is φ = 21353280.

The previous prime is 21353279. The next prime is 21353347. The reversal of 21353281 is 18235312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19891600 + 1461681 = 4460^2 + 1209^2 .

It is a cyclic number.

It is not a de Polignac number, because 21353281 - 2¹ = 21353279 is a prime.

It is a super-2 number, since 2×21353281² = 911925218929922, which contains 22 as substring.

Together with 21353279, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21353201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10676640 + 10676641.

It is an arithmetic number, because the mean of its divisors is an integer number (10676641).

Almost surely, 2^21353281 is an apocalyptic number.

It is an amenable number.

21353281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21353281 is an equidigital number, since it uses as much as digits as its factorization.

21353281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 25.

The square root of 21353281 is about 4620.9610472282. The cubic root of 21353281 is about 277.4309261837.

Adding to 21353281 its reverse (18235312), we get a palindrome (39588593).

The spelling of 21353281 in words is "twenty-one million, three hundred fifty-three thousand, two hundred eighty-one".