162561991 has 2 divisors, whose sum is σ = 162561992. Its totient is φ = 162561990.

The previous prime is 162561989. The next prime is 162562027. The reversal of 162561991 is 199165261.

It is a weak prime.

It is an emirp because it is prime and its reverse (199165261) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 162561991 - 2¹ = 162561989 is a prime.

Together with 162561989, it forms a pair of twin primes.

It is equal to p_9109957 and since 162561991 and 9109957 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 (162561901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81280995 + 81280996.

It is an arithmetic number, because the mean of its divisors is an integer number (81280996).

Almost surely, 2^162561991 is an apocalyptic number.

162561991 is a deficient number, since it is larger than the sum of its proper divisors (1).

162561991 is an equidigital number, since it uses as much as digits as its factorization.

162561991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 29160, while the sum is 40.

The square root of 162561991 is about 12749.9800392001. The cubic root of 162561991 is about 545.7658240277.

The spelling of 162561991 in words is "one hundred sixty-two million, five hundred sixty-one thousand, nine hundred ninety-one".