9891781 has 2 divisors, whose sum is σ = 9891782. Its totient is φ = 9891780.

The previous prime is 9891779. The next prime is 9891793. The reversal of 9891781 is 1871989.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6502500 + 3389281 = 2550^2 + 1841^2 .

It is a cyclic number.

It is not a de Polignac number, because 9891781 - 2¹ = 9891779 is a prime.

It is a super-2 number, since 2×9891781² = 195694662703922, which contains 22 as substring.

Together with 9891779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9891731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4945890 + 4945891.

It is an arithmetic number, because the mean of its divisors is an integer number (4945891).

Almost surely, 2^9891781 is an apocalyptic number.

It is an amenable number.

9891781 is a deficient number, since it is larger than the sum of its proper divisors (1).

9891781 is an equidigital number, since it uses as much as digits as its factorization.

9891781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 43.

The square root of 9891781 is about 3145.1201884825. The cubic root of 9891781 is about 214.6634793173.

The spelling of 9891781 in words is "nine million, eight hundred ninety-one thousand, seven hundred eighty-one".