21240313 has 2 divisors, whose sum is σ = 21240314. Its totient is φ = 21240312.

The previous prime is 21240311. The next prime is 21240377. The reversal of 21240313 is 31304212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20548089 + 692224 = 4533^2 + 832^2 .

It is a cyclic number.

It is not a de Polignac number, because 21240313 - 2¹ = 21240311 is a prime.

Together with 21240311, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21240311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10620156 + 10620157.

It is an arithmetic number, because the mean of its divisors is an integer number (10620157).

Almost surely, 2^21240313 is an apocalyptic number.

It is an amenable number.

21240313 is a deficient number, since it is larger than the sum of its proper divisors (1).

21240313 is an equidigital number, since it uses as much as digits as its factorization.

21240313 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21240313 is about 4608.7214062037. The cubic root of 21240313 is about 276.9408180724.

Adding to 21240313 its reverse (31304212), we get a palindrome (52544525).

The spelling of 21240313 in words is "twenty-one million, two hundred forty thousand, three hundred thirteen".