165720281 has 4 divisors (see below), whose sum is σ = 165756432. Its totient is φ = 165684132.

The previous prime is 165720277. The next prime is 165720287. The reversal of 165720281 is 182027561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 165720281 - 2² = 165720277 is a prime.

It is a super-3 number, since 3×165720281³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165720287) 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 in 3 ways as a sum of consecutive naturals, for example, 9995 + ... + 20768.

It is an arithmetic number, because the mean of its divisors is an integer number (41439108).

Almost surely, 2^165720281 is an apocalyptic number.

It is an amenable number.

165720281 is a deficient number, since it is larger than the sum of its proper divisors (36151).

165720281 is an equidigital number, since it uses as much as digits as its factorization.

165720281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36150.

The product of its (nonzero) digits is 6720, while the sum is 32.

The square root of 165720281 is about 12873.2389475221. The cubic root of 165720281 is about 549.2775981274.

The spelling of 165720281 in words is "one hundred sixty-five million, seven hundred twenty thousand, two hundred eighty-one".