21243361 has 2 divisors, whose sum is σ = 21243362. Its totient is φ = 21243360.

The previous prime is 21243359. The next prime is 21243403. The reversal of 21243361 is 16334212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15555136 + 5688225 = 3944^2 + 2385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21243361 - 2¹ = 21243359 is a prime.

Together with 21243359, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21243331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621680 + 10621681.

It is an arithmetic number, because the mean of its divisors is an integer number (10621681).

Almost surely, 2^21243361 is an apocalyptic number.

It is an amenable number.

21243361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243361 is an equidigital number, since it uses as much as digits as its factorization.

21243361 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 22.

The square root of 21243361 is about 4609.0520717388. The cubic root of 21243361 is about 276.9540645068.

Adding to 21243361 its reverse (16334212), we get a palindrome (37577573).

The spelling of 21243361 in words is "twenty-one million, two hundred forty-three thousand, three hundred sixty-one".