165845521 has 4 divisors (see below), whose sum is σ = 165906544. Its totient is φ = 165784500.

The previous prime is 165845501. The next prime is 165845531. The reversal of 165845521 is 125548561.

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: 125548561 = 19 ⋅6607819.

It is a cyclic number.

It is not a de Polignac number, because 165845521 - 2¹⁷ = 165714449 is a prime.

It is a super-2 number, since 2×165845521² = 55009473671522882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165845501) 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, 26235 + ... + 31936.

It is an arithmetic number, because the mean of its divisors is an integer number (41476636).

Almost surely, 2^165845521 is an apocalyptic number.

It is an amenable number.

165845521 is a deficient number, since it is larger than the sum of its proper divisors (61023).

165845521 is an equidigital number, since it uses as much as digits as its factorization.

165845521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61022.

The product of its digits is 48000, while the sum is 37.

The square root of 165845521 is about 12878.1023835036. The cubic root of 165845521 is about 549.4159320395.

The spelling of 165845521 in words is "one hundred sixty-five million, eight hundred forty-five thousand, five hundred twenty-one".