999999818878789 has 2 divisors, whose sum is σ = 999999818878790. Its totient is φ = 999999818878788.

The previous prime is 999999818878663. The next prime is 999999818878873. The reversal of 999999818878789 is 987878818999999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 988550000676225 + 11449818202564 = 31441215^2 + 3383758^2 .

It is a cyclic number.

It is not a de Polignac number, because 999999818878789 - 2⁴⁷ = 859262330523461 is a prime.

It is a super-2 number, since 2×999999818878789² (a number of 31 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999999818878889) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499999909439394 + 499999909439395.

It is an arithmetic number, because the mean of its divisors is an integer number (499999909439395).

Almost surely, 2^{999999818878789} is an apocalyptic number.

It is an amenable number.

999999818878789 is a deficient number, since it is larger than the sum of its proper divisors (1).

999999818878789 is an equidigital number, since it uses as much as digits as its factorization.

999999818878789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7679688081408, while the sum is 118.

The spelling of 999999818878789 in words is "nine hundred ninety-nine trillion, nine hundred ninety-nine billion, eight hundred eighteen million, eight hundred seventy-eight thousand, seven hundred eighty-nine".