165787321 has 4 divisors (see below), whose sum is σ = 189471232. Its totient is φ = 142103412.

The previous prime is 165787319. The next prime is 165787327. The reversal of 165787321 is 123787561.

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, and also an emirpimes, since its reverse is a distinct semiprime: 123787561 = 149 ⋅830789.

It is a cyclic number.

It is not a de Polignac number, because 165787321 - 2¹ = 165787319 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165787327) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11841945 + ... + 11841958.

It is an arithmetic number, because the mean of its divisors is an integer number (47367808).

Almost surely, 2^165787321 is an apocalyptic number.

It is an amenable number.

165787321 is a deficient number, since it is larger than the sum of its proper divisors (23683911).

165787321 is an equidigital number, since it uses as much as digits as its factorization.

165787321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23683910.

The product of its digits is 70560, while the sum is 40.

The square root of 165787321 is about 12875.8425355392. The cubic root of 165787321 is about 549.3516558621.

The spelling of 165787321 in words is "one hundred sixty-five million, seven hundred eighty-seven thousand, three hundred twenty-one".