21123313 has 2 divisors, whose sum is σ = 21123314. Its totient is φ = 21123312.

The previous prime is 21123301. The next prime is 21123331. The reversal of 21123313 is 31332112.

Together with next prime (21123331) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15586704 + 5536609 = 3948^2 + 2353^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123313 is a prime.

It is not a weakly prime, because it can be changed into another prime (21123373) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561656 + 10561657.

It is an arithmetic number, because the mean of its divisors is an integer number (10561657).

Almost surely, 2^21123313 is an apocalyptic number.

It is an amenable number.

21123313 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123313 is an equidigital number, since it uses as much as digits as its factorization.

21123313 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108, while the sum is 16.

The square root of 21123313 is about 4596.0105526424. The cubic root of 21123313 is about 276.4313818742.

Adding to 21123313 its reverse (31332112), we get a palindrome (52455425).

The spelling of 21123313 in words is "twenty-one million, one hundred twenty-three thousand, three hundred thirteen".