165740621 has 4 divisors (see below), whose sum is σ = 165785532. Its totient is φ = 165695712.

The previous prime is 165740611. The next prime is 165740623. The reversal of 165740621 is 126047561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 126047561 = 47 ⋅2681863.

It can be written as a sum of positive squares in 2 ways, for example, as 138062500 + 27678121 = 11750^2 + 5261^2 .

It is a cyclic number.

It is not a de Polignac number, because 165740621 - 2⁶ = 165740557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165740623) 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, 16370 + ... + 24483.

It is an arithmetic number, because the mean of its divisors is an integer number (41446383).

Almost surely, 2^165740621 is an apocalyptic number.

It is an amenable number.

165740621 is a deficient number, since it is larger than the sum of its proper divisors (44911).

165740621 is an equidigital number, since it uses as much as digits as its factorization.

165740621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44910.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 165740621 is about 12874.0289342536. The cubic root of 165740621 is about 549.3000694251.

The spelling of 165740621 in words is "one hundred sixty-five million, seven hundred forty thousand, six hundred twenty-one".