21331313 has 2 divisors, whose sum is σ = 21331314. Its totient is φ = 21331312.

The previous prime is 21331309. The next prime is 21331333. The reversal of 21331313 is 31313312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18809569 + 2521744 = 4337^2 + 1588^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331313 - 2² = 21331309 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21331291 and 21331300.

It is not a weakly prime, because it can be changed into another prime (21331333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665656 + 10665657.

It is an arithmetic number, because the mean of its divisors is an integer number (10665657).

Almost surely, 2^21331313 is an apocalyptic number.

It is an amenable number.

21331313 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331313 is an equidigital number, since it uses as much as digits as its factorization.

21331313 is an evil number, because the sum of its binary digits is even.

The product of its digits is 162, while the sum is 17.

The square root of 21331313 is about 4618.5834408398. The cubic root of 21331313 is about 277.3357543333.

Adding to 21331313 its reverse (31313312), we get a palindrome (52644625).

The spelling of 21331313 in words is "twenty-one million, three hundred thirty-one thousand, three hundred thirteen".