8991661993 has 2 divisors, whose sum is σ = 8991661994. Its totient is φ = 8991661992.

The previous prime is 8991661963. The next prime is 8991662039. The reversal of 8991661993 is 3991661998.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6973586064 + 2018075929 = 83508^2 + 44923^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8991661993 is a prime.

It is not a weakly prime, because it can be changed into another prime (8991661963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4495830996 + 4495830997.

It is an arithmetic number, because the mean of its divisors is an integer number (4495830997).

Almost surely, 2^8991661993 is an apocalyptic number.

It is an amenable number.

8991661993 is a deficient number, since it is larger than the sum of its proper divisors (1).

8991661993 is an equidigital number, since it uses as much as digits as its factorization.

8991661993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5668704, while the sum is 61.

The square root of 8991661993 is about 94824.3744666950. The cubic root of 8991661993 is about 2079.4412633390.

The spelling of 8991661993 in words is "eight billion, nine hundred ninety-one million, six hundred sixty-one thousand, nine hundred ninety-three".