817768981 has 2 divisors, whose sum is σ = 817768982. Its totient is φ = 817768980.

The previous prime is 817768967. The next prime is 817768997. The reversal of 817768981 is 189867718.

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., 472366756 + 345402225 = 21734^2 + 18585^2 .

It is a cyclic number.

It is not a de Polignac number, because 817768981 - 2¹³ = 817760789 is a prime.

It is a super-2 number, since 2×817768981² = 1337492212571556722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (817768921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408884490 + 408884491.

It is an arithmetic number, because the mean of its divisors is an integer number (408884491).

Almost surely, 2^817768981 is an apocalyptic number.

It is an amenable number.

817768981 is a deficient number, since it is larger than the sum of its proper divisors (1).

817768981 is an equidigital number, since it uses as much as digits as its factorization.

817768981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1354752, while the sum is 55.

The square root of 817768981 is about 28596.6603120015. The cubic root of 817768981 is about 935.1405246957.

The spelling of 817768981 in words is "eight hundred seventeen million, seven hundred sixty-eight thousand, nine hundred eighty-one".