1189551991 has 2 divisors, whose sum is σ = 1189551992. Its totient is φ = 1189551990.

The previous prime is 1189551967. The next prime is 1189552027. The reversal of 1189551991 is 1991559811.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1189551991 - 2⁹ = 1189551479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1189551091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 594775995 + 594775996.

It is an arithmetic number, because the mean of its divisors is an integer number (594775996).

Almost surely, 2^1189551991 is an apocalyptic number.

1189551991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1189551991 is an equidigital number, since it uses as much as digits as its factorization.

1189551991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145800, while the sum is 49.

The square root of 1189551991 is about 34489.8824439864. The cubic root of 1189551991 is about 1059.5655009884.

The spelling of 1189551991 in words is "one billion, one hundred eighty-nine million, five hundred fifty-one thousand, nine hundred ninety-one".