191891989 has 2 divisors, whose sum is σ = 191891990. Its totient is φ = 191891988.

The previous prime is 191891983. The next prime is 191892017. The reversal of 191891989 is 989198191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 131285764 + 60606225 = 11458^2 + 7785^2 .

It is a cyclic number.

It is not a de Polignac number, because 191891989 - 2¹⁷ = 191760917 is a prime.

It is a super-2 number, since 2×191891989² = 73645070884752242, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191891983) 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, 95945994 + 95945995.

It is an arithmetic number, because the mean of its divisors is an integer number (95945995).

Almost surely, 2^191891989 is an apocalyptic number.

It is an amenable number.

191891989 is a deficient number, since it is larger than the sum of its proper divisors (1).

191891989 is an equidigital number, since it uses as much as digits as its factorization.

191891989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 419904, while the sum is 55.

The square root of 191891989 is about 13852.5084010081. The cubic root of 191891989 is about 576.7916280959.

The spelling of 191891989 in words is "one hundred ninety-one million, eight hundred ninety-one thousand, nine hundred eighty-nine".