21247313 has 2 divisors, whose sum is σ = 21247314. Its totient is φ = 21247312.

The previous prime is 21247309. The next prime is 21247319. The reversal of 21247313 is 31374212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20866624 + 380689 = 4568^2 + 617^2 .

It is a cyclic number.

It is not a de Polignac number, because 21247313 - 2² = 21247309 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21247319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10623656 + 10623657.

It is an arithmetic number, because the mean of its divisors is an integer number (10623657).

Almost surely, 2^21247313 is an apocalyptic number.

It is an amenable number.

21247313 is a deficient number, since it is larger than the sum of its proper divisors (1).

21247313 is an equidigital number, since it uses as much as digits as its factorization.

21247313 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1008, while the sum is 23.

The square root of 21247313 is about 4609.4807733627. The cubic root of 21247313 is about 276.9712377874.

The spelling of 21247313 in words is "twenty-one million, two hundred forty-seven thousand, three hundred thirteen".