163721 has 4 divisors (see below), whose sum is σ = 165444. Its totient is φ = 162000.

The previous prime is 163697. The next prime is 163729. The reversal of 163721 is 127361.

It is a happy number.

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 144400 + 19321 = 380^2 + 139^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-163721 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 163693 and 163702.

It is not an unprimeable number, because it can be changed into a prime (163729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 710 + ... + 911.

It is an arithmetic number, because the mean of its divisors is an integer number (41361).

2¹⁶³⁷²¹ is an apocalyptic number.

It is an amenable number.

163721 is a deficient number, since it is larger than the sum of its proper divisors (1723).

163721 is a wasteful number, since it uses less digits than its factorization.

163721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1722.

The product of its digits is 252, while the sum is 20.

The square root of 163721 is about 404.6245172997. The cubic root of 163721 is about 54.7059792244.

It can be divided in two parts, 16 and 3721, that multiplied together give a square (59536 = 244²).

The spelling of 163721 in words is "one hundred sixty-three thousand, seven hundred twenty-one".