163961921 has 4 divisors (see below), whose sum is σ = 164521812. Its totient is φ = 163402032.

The previous prime is 163961909. The next prime is 163961947. The reversal of 163961921 is 129169361.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 110145025 + 53816896 = 10495^2 + 7336^2 .

It is a cyclic number.

It is not a de Polignac number, because 163961921 - 2⁶ = 163961857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (163961951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 279506 + ... + 280091.

It is an arithmetic number, because the mean of its divisors is an integer number (41130453).

Almost surely, 2^163961921 is an apocalyptic number.

It is an amenable number.

163961921 is a deficient number, since it is larger than the sum of its proper divisors (559891).

163961921 is an equidigital number, since it uses as much as digits as its factorization.

163961921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 559890.

The product of its digits is 17496, while the sum is 38.

The square root of 163961921 is about 12804.7616533850. The cubic root of 163961921 is about 547.3279997367.

The spelling of 163961921 in words is "one hundred sixty-three million, nine hundred sixty-one thousand, nine hundred twenty-one".