165836381821 has 4 divisors (see below), whose sum is σ = 180912416544. Its totient is φ = 150760347100.

The previous prime is 165836381819. The next prime is 165836381827. The reversal of 165836381821 is 128183638561.

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 not a de Polignac number, because 165836381821 - 2¹ = 165836381819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165836381827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7538017345 + ... + 7538017366.

It is an arithmetic number, because the mean of its divisors is an integer number (45228104136).

Almost surely, 2^165836381821 is an apocalyptic number.

165836381821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

165836381821 is a deficient number, since it is larger than the sum of its proper divisors (15076034723).

165836381821 is a wasteful number, since it uses less digits than its factorization.

165836381821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15076034722.

The product of its digits is 1658880, while the sum is 52.

The spelling of 165836381821 in words is "one hundred sixty-five billion, eight hundred thirty-six million, three hundred eighty-one thousand, eight hundred twenty-one".