9891457781 has 2 divisors, whose sum is σ = 9891457782. Its totient is φ = 9891457780.

The previous prime is 9891457753. The next prime is 9891457783. The reversal of 9891457781 is 1877541989.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8402655556 + 1488802225 = 91666^2 + 38585^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9891457781 is a prime.

It is a super-2 number, since 2×9891457781² (a number of 21 digits) contains 22 as substring.

Together with 9891457783, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 9891457781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9891457783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4945728890 + 4945728891.

It is an arithmetic number, because the mean of its divisors is an integer number (4945728891).

Almost surely, 2^9891457781 is an apocalyptic number.

It is an amenable number.

9891457781 is a deficient number, since it is larger than the sum of its proper divisors (1).

9891457781 is an equidigital number, since it uses as much as digits as its factorization.

9891457781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5080320, while the sum is 59.

The square root of 9891457781 is about 99455.8081813224. The cubic root of 9891457781 is about 2146.6114121222.

The spelling of 9891457781 in words is "nine billion, eight hundred ninety-one million, four hundred fifty-seven thousand, seven hundred eighty-one".