159621991 has 2 divisors, whose sum is σ = 159621992. Its totient is φ = 159621990.

The previous prime is 159621989. The next prime is 159622013. The reversal of 159621991 is 199126951.

159621991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is an emirp because it is prime and its reverse (199126951) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 159621991 - 2¹ = 159621989 is a prime.

Together with 159621989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (159621911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 79810995 + 79810996.

It is an arithmetic number, because the mean of its divisors is an integer number (79810996).

Almost surely, 2^159621991 is an apocalyptic number.

159621991 is a deficient number, since it is larger than the sum of its proper divisors (1).

159621991 is an equidigital number, since it uses as much as digits as its factorization.

159621991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 43740, while the sum is 43.

The square root of 159621991 is about 12634.1596871339. The cubic root of 159621991 is about 542.4556552340.

The spelling of 159621991 in words is "one hundred fifty-nine million, six hundred twenty-one thousand, nine hundred ninety-one".