165720881 has 2 divisors, whose sum is σ = 165720882. Its totient is φ = 165720880.

The previous prime is 165720853. The next prime is 165720883. The reversal of 165720881 is 188027561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 159390625 + 6330256 = 12625^2 + 2516^2 .

It is a cyclic number.

It is not a de Polignac number, because 165720881 - 2¹⁰ = 165719857 is a prime.

It is a super-2 number, since 2×165720881² = 54926820798832322, which contains 22 as substring.

Together with 165720883, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (165720883) 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, 82860440 + 82860441.

It is an arithmetic number, because the mean of its divisors is an integer number (82860441).

Almost surely, 2^165720881 is an apocalyptic number.

It is an amenable number.

165720881 is a deficient number, since it is larger than the sum of its proper divisors (1).

165720881 is an equidigital number, since it uses as much as digits as its factorization.

165720881 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 26880, while the sum is 38.

The square root of 165720881 is about 12873.2622516594. The cubic root of 165720881 is about 549.2782610239.

The spelling of 165720881 in words is "one hundred sixty-five million, seven hundred twenty thousand, eight hundred eighty-one".