165810021 has 16 divisors (see below), whose sum is σ = 243625536. Its totient is φ = 99662976.

The previous prime is 165810011. The next prime is 165810067. The reversal of 165810021 is 120018561.

165810021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 165810021 - 2¹¹ = 165807973 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 165809973 and 165810000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165810011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47760 + ... + 51113.

It is an arithmetic number, because the mean of its divisors is an integer number (15226596).

Almost surely, 2^165810021 is an apocalyptic number.

It is an amenable number.

165810021 is a deficient number, since it is larger than the sum of its proper divisors (77815515).

165810021 is a wasteful number, since it uses less digits than its factorization.

165810021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98932.

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 165810021 is about 12876.7240010804. The cubic root of 165810021 is about 549.3767275692.

Adding to 165810021 its reverse (120018561), we get a palindrome (285828582).

The spelling of 165810021 in words is "one hundred sixty-five million, eight hundred ten thousand, twenty-one".