158581991 has 2 divisors, whose sum is σ = 158581992. Its totient is φ = 158581990.

The previous prime is 158581949. The next prime is 158582023. The reversal of 158581991 is 199185851.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 158581991 - 2²² = 154387687 is a prime.

It is a Sophie Germain prime.

It is equal to p_8899355 and since 158581991 and 8899355 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (158581091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 79290995 + 79290996.

It is an arithmetic number, because the mean of its divisors is an integer number (79290996).

Almost surely, 2^158581991 is an apocalyptic number.

158581991 is a deficient number, since it is larger than the sum of its proper divisors (1).

158581991 is an equidigital number, since it uses as much as digits as its factorization.

158581991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 129600, while the sum is 47.

The square root of 158581991 is about 12592.9341696048. The cubic root of 158581991 is about 541.2749834059.

The spelling of 158581991 in words is "one hundred fifty-eight million, five hundred eighty-one thousand, nine hundred ninety-one".