1000009999981 has 2 divisors, whose sum is σ = 1000009999982. Its totient is φ = 1000009999980.

The previous prime is 1000009999951. The next prime is 1000010000023. The reversal of 1000009999981 is 1899999000001.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 723365559081 + 276644440900 = 850509^2 + 525970^2 .

It is an emirp because it is prime and its reverse (1899999000001) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1000009999981 - 2⁵ = 1000009999949 is a prime.

It is a super-2 number, since 2×1000009999981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1000009999951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 500004999990 + 500004999991.

It is an arithmetic number, because the mean of its divisors is an integer number (500004999991).

Almost surely, 2^{1000009999981} is an apocalyptic number.

It is an amenable number.

1000009999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1000009999981 is an equidigital number, since it uses as much as digits as its factorization.

1000009999981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 472392, while the sum is 55.

The spelling of 1000009999981 in words is "one trillion, nine million, nine hundred ninety-nine thousand, nine hundred eighty-one".