1189021991 has 2 divisors, whose sum is σ = 1189021992. Its totient is φ = 1189021990.

The previous prime is 1189021979. The next prime is 1189021997. The reversal of 1189021991 is 1991209811.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1189021991 - 2⁶ = 1189021927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1189021997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 594510995 + 594510996.

It is an arithmetic number, because the mean of its divisors is an integer number (594510996).

Almost surely, 2^1189021991 is an apocalyptic number.

1189021991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1189021991 is an equidigital number, since it uses as much as digits as its factorization.

1189021991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 41.

The square root of 1189021991 is about 34482.1981752904. The cubic root of 1189021991 is about 1059.4081159275.

The spelling of 1189021991 in words is "one billion, one hundred eighty-nine million, twenty-one thousand, nine hundred ninety-one".