817744987993 has 2 divisors, whose sum is σ = 817744987994. Its totient is φ = 817744987992.

The previous prime is 817744987991. The next prime is 817744988003. The reversal of 817744987993 is 399789447718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 567171659664 + 250573328329 = 753108^2 + 500573^2 .

It is a cyclic number.

It is not a de Polignac number, because 817744987993 - 2¹ = 817744987991 is a prime.

Together with 817744987991, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (817744987991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408872493996 + 408872493997.

It is an arithmetic number, because the mean of its divisors is an integer number (408872493997).

Almost surely, 2^817744987993 is an apocalyptic number.

It is an amenable number.

817744987993 is a deficient number, since it is larger than the sum of its proper divisors (1).

817744987993 is an equidigital number, since it uses as much as digits as its factorization.

817744987993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 768144384, while the sum is 76.

The spelling of 817744987993 in words is "eight hundred seventeen billion, seven hundred forty-four million, nine hundred eighty-seven thousand, nine hundred ninety-three".