9181981 has 2 divisors, whose sum is σ = 9181982. Its totient is φ = 9181980.

The previous prime is 9181979. The next prime is 9181987. The reversal of 9181981 is 1891819.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6175225 + 3006756 = 2485^2 + 1734^2 .

It is a cyclic number.

It is not a de Polignac number, because 9181981 - 2¹ = 9181979 is a prime.

It is a super-2 number, since 2×9181981² = 168617550168722, which contains 22 as substring.

Together with 9181979, it forms a pair of twin primes.

9181981 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 9181981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9181987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4590990 + 4590991.

It is an arithmetic number, because the mean of its divisors is an integer number (4590991).

Almost surely, 2^9181981 is an apocalyptic number.

It is an amenable number.

9181981 is a deficient number, since it is larger than the sum of its proper divisors (1).

9181981 is an equidigital number, since it uses as much as digits as its factorization.

9181981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 37.

The square root of 9181981 is about 3030.1783775877. The cubic root of 9181981 is about 209.4010218196.

The spelling of 9181981 in words is "nine million, one hundred eighty-one thousand, nine hundred eighty-one".