1989116861 has 2 divisors, whose sum is σ = 1989116862. Its totient is φ = 1989116860.

The previous prime is 1989116851. The next prime is 1989116863. The reversal of 1989116861 is 1686119891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1978915225 + 10201636 = 44485^2 + 3194^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1989116861 is a prime.

Together with 1989116863, it forms a pair of twin primes.

It is a Chen prime.

1989116861 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1989116863) 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, 994558430 + 994558431.

It is an arithmetic number, because the mean of its divisors is an integer number (994558431).

Almost surely, 2^1989116861 is an apocalyptic number.

It is an amenable number.

1989116861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1989116861 is an equidigital number, since it uses as much as digits as its factorization.

1989116861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 50.

The square root of 1989116861 is about 44599.5163763017. The cubic root of 1989116861 is about 1257.6315760967.

The spelling of 1989116861 in words is "one billion, nine hundred eighty-nine million, one hundred sixteen thousand, eight hundred sixty-one".