9987891281 has 2 divisors, whose sum is σ = 9987891282. Its totient is φ = 9987891280.

The previous prime is 9987891269. The next prime is 9987891283. The reversal of 9987891281 is 1821987899.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5138022400 + 4849868881 = 71680^2 + 69641^2 .

It is an emirp because it is prime and its reverse (1821987899) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 9987891281 - 2⁶ = 9987891217 is a prime.

It is a super-2 number, since 2×9987891281² (a number of 21 digits) contains 22 as substring.

Together with 9987891283, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (9987891283) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4993945640 + 4993945641.

It is an arithmetic number, because the mean of its divisors is an integer number (4993945641).

Almost surely, 2^9987891281 is an apocalyptic number.

It is an amenable number.

9987891281 is a deficient number, since it is larger than the sum of its proper divisors (1).

9987891281 is an equidigital number, since it uses as much as digits as its factorization.

9987891281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5225472, while the sum is 62.

The square root of 9987891281 is about 99939.4380662609. The cubic root of 9987891281 is about 2153.5647573361.

The spelling of 9987891281 in words is "nine billion, nine hundred eighty-seven million, eight hundred ninety-one thousand, two hundred eighty-one".