21140813 has 2 divisors, whose sum is σ = 21140814. Its totient is φ = 21140812.

The previous prime is 21140807. The next prime is 21140827. The reversal of 21140813 is 31804112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20912329 + 228484 = 4573^2 + 478^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21140813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21140893) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10570406 + 10570407.

It is an arithmetic number, because the mean of its divisors is an integer number (10570407).

Almost surely, 2^21140813 is an apocalyptic number.

It is an amenable number.

21140813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21140813 is an equidigital number, since it uses as much as digits as its factorization.

21140813 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21140813 is about 4597.9139835364. The cubic root of 21140813 is about 276.5076990358.

Adding to 21140813 its reverse (31804112), we get a palindrome (52944925).

The spelling of 21140813 in words is "twenty-one million, one hundred forty thousand, eight hundred thirteen".