999987999781 has 2 divisors, whose sum is σ = 999987999782. Its totient is φ = 999987999780.

The previous prime is 999987999761. The next prime is 999987999817. The reversal of 999987999781 is 187999789999.

Together with next prime (999987999817) 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., 990839077281 + 9148922500 = 995409^2 + 95650^2 .

It is a cyclic number.

It is not a de Polignac number, because 999987999781 - 2²⁹ = 999451128869 is a prime.

It is a super-2 number, since 2×999987999781² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 999987999781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999987999761) 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, 499993999890 + 499993999891.

It is an arithmetic number, because the mean of its divisors is an integer number (499993999891).

Almost surely, 2^999987999781 is an apocalyptic number.

It is an amenable number.

999987999781 is a deficient number, since it is larger than the sum of its proper divisors (1).

999987999781 is an equidigital number, since it uses as much as digits as its factorization.

999987999781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14999390784, while the sum is 94.

The spelling of 999987999781 in words is "nine hundred ninety-nine billion, nine hundred eighty-seven million, nine hundred ninety-nine thousand, seven hundred eighty-one".