21643313 has 2 divisors, whose sum is σ = 21643314. Its totient is φ = 21643312.

The previous prime is 21643289. The next prime is 21643331. The reversal of 21643313 is 31334612.

Together with next prime (21643331) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21641104 + 2209 = 4652^2 + 47^2 .

It is a cyclic number.

It is not a de Polignac number, because 21643313 - 2¹⁰ = 21642289 is a prime.

It is not a weakly prime, because it can be changed into another prime (21643333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821656 + 10821657.

It is an arithmetic number, because the mean of its divisors is an integer number (10821657).

Almost surely, 2^21643313 is an apocalyptic number.

It is an amenable number.

21643313 is a deficient number, since it is larger than the sum of its proper divisors (1).

21643313 is an equidigital number, since it uses as much as digits as its factorization.

21643313 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 23.

The square root of 21643313 is about 4652.2374187051. The cubic root of 21643313 is about 278.6813549322.

Adding to 21643313 its reverse (31334612), we get a palindrome (52977925).

The spelling of 21643313 in words is "twenty-one million, six hundred forty-three thousand, three hundred thirteen".