1989445891 has 2 divisors, whose sum is σ = 1989445892. Its totient is φ = 1989445890.

The previous prime is 1989445889. The next prime is 1989445897. The reversal of 1989445891 is 1985449891.

It is a weak prime.

It is an emirp because it is prime and its reverse (1985449891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1989445891 - 2¹ = 1989445889 is a prime.

Together with 1989445889, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1989445897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 994722945 + 994722946.

It is an arithmetic number, because the mean of its divisors is an integer number (994722946).

Almost surely, 2^1989445891 is an apocalyptic number.

1989445891 is a deficient number, since it is larger than the sum of its proper divisors (1).

1989445891 is an equidigital number, since it uses as much as digits as its factorization.

1989445891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3732480, while the sum is 58.

The square root of 1989445891 is about 44603.2049409008. The cubic root of 1989445891 is about 1257.7009160320.

The spelling of 1989445891 in words is "one billion, nine hundred eighty-nine million, four hundred forty-five thousand, eight hundred ninety-one".