165415981 has 2 divisors, whose sum is σ = 165415982. Its totient is φ = 165415980.

The previous prime is 165415979. The next prime is 165415993. The reversal of 165415981 is 189514561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 115218756 + 50197225 = 10734^2 + 7085^2 .

It is a cyclic number.

It is not a de Polignac number, because 165415981 - 2¹ = 165415979 is a prime.

It is a super-2 number, since 2×165415981² = 54724893540384722, which contains 22 as substring.

Together with 165415979, 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 (165415951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82707990 + 82707991.

It is an arithmetic number, because the mean of its divisors is an integer number (82707991).

Almost surely, 2^165415981 is an apocalyptic number.

It is an amenable number.

165415981 is a deficient number, since it is larger than the sum of its proper divisors (1).

165415981 is an equidigital number, since it uses as much as digits as its factorization.

165415981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43200, while the sum is 40.

The square root of 165415981 is about 12861.4144245491. The cubic root of 165415981 is about 548.9411927459.

It can be divided in two parts, 16541 and 5981, that added together give a palindrome (22522).

The spelling of 165415981 in words is "one hundred sixty-five million, four hundred fifteen thousand, nine hundred eighty-one".