21821768513 has 2 divisors, whose sum is σ = 21821768514. Its totient is φ = 21821768512.

The previous prime is 21821768491. The next prime is 21821768519. The reversal of 21821768513 is 31586712812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18788733184 + 3033035329 = 137072^2 + 55073^2 .

It is a cyclic number.

It is not a de Polignac number, because 21821768513 - 2¹⁴ = 21821752129 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21821768519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10910884256 + 10910884257.

It is an arithmetic number, because the mean of its divisors is an integer number (10910884257).

Almost surely, 2^21821768513 is an apocalyptic number.

It is an amenable number.

21821768513 is a deficient number, since it is larger than the sum of its proper divisors (1).

21821768513 is an equidigital number, since it uses as much as digits as its factorization.

21821768513 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 161280, while the sum is 44.

The spelling of 21821768513 in words is "twenty-one billion, eight hundred twenty-one million, seven hundred sixty-eight thousand, five hundred thirteen".