163173721 has 8 divisors (see below), whose sum is σ = 164763720. Its totient is φ = 161591808.

The previous prime is 163173683. The next prime is 163173779. The reversal of 163173721 is 127371361.

It can be written as a sum of positive squares in 4 ways, for example, as 54597321 + 108576400 = 7389^2 + 10420^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 163173721 - 2¹⁵ = 163140953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (163173781) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43305 + ... + 46921.

It is an arithmetic number, because the mean of its divisors is an integer number (20595465).

Almost surely, 2^163173721 is an apocalyptic number.

It is an amenable number.

163173721 is a deficient number, since it is larger than the sum of its proper divisors (1589999).

163173721 is a wasteful number, since it uses less digits than its factorization.

163173721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4043.

The product of its digits is 5292, while the sum is 31.

The square root of 163173721 is about 12773.9469624701. The cubic root of 163173721 is about 546.4495497028.

The spelling of 163173721 in words is "one hundred sixty-three million, one hundred seventy-three thousand, seven hundred twenty-one".