21991803448393 has 2 divisors, whose sum is σ = 21991803448394. Its totient is φ = 21991803448392.

The previous prime is 21991803448339. The next prime is 21991803448523. The reversal of 21991803448393 is 39384430819912.

Together with previous prime (21991803448339) 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., 21940352506809 + 51450941584 = 4684053^2 + 226828^2 .

It is a cyclic number.

It is not a de Polignac number, because 21991803448393 - 2¹⁷ = 21991803317321 is a prime.

It is not a weakly prime, because it can be changed into another prime (21991803448193) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10995901724196 + 10995901724197.

It is an arithmetic number, because the mean of its divisors is an integer number (10995901724197).

Almost surely, 2^{21991803448393} is an apocalyptic number.

It is an amenable number.

21991803448393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21991803448393 is an equidigital number, since it uses as much as digits as its factorization.

21991803448393 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40310784, while the sum is 64.

The spelling of 21991803448393 in words is "twenty-one trillion, nine hundred ninety-one billion, eight hundred three million, four hundred forty-eight thousand, three hundred ninety-three".