9851998781 has 2 divisors, whose sum is σ = 9851998782. Its totient is φ = 9851998780.

The previous prime is 9851998759. The next prime is 9851998811. The reversal of 9851998781 is 1878991589.

9851998781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9727876900 + 124121881 = 98630^2 + 11141^2 .

It is a cyclic number.

It is not a de Polignac number, because 9851998781 - 2³⁰ = 8778256957 is a prime.

It is a super-2 number, since 2×9851998781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9851998381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4925999390 + 4925999391.

It is an arithmetic number, because the mean of its divisors is an integer number (4925999391).

Almost surely, 2^9851998781 is an apocalyptic number.

It is an amenable number.

9851998781 is a deficient number, since it is larger than the sum of its proper divisors (1).

9851998781 is an equidigital number, since it uses as much as digits as its factorization.

9851998781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13063680, while the sum is 65.

The square root of 9851998781 is about 99257.2354088104. The cubic root of 9851998781 is about 2143.7531875662.

The spelling of 9851998781 in words is "nine billion, eight hundred fifty-one million, nine hundred ninety-eight thousand, seven hundred eighty-one".