161720 has 32 divisors (see below), whose sum is σ = 393120. Its totient is φ = 59520.

The previous prime is 161717. The next prime is 161729. The reversal of 161720 is 27161.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161729) 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 7 ways as a sum of consecutive naturals, for example, 365 + ... + 675.

It is an arithmetic number, because the mean of its divisors is an integer number (12285).

2¹⁶¹⁷²⁰ is an apocalyptic number.

161720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 161720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (196560).

161720 is an abundant number, since it is smaller than the sum of its proper divisors (231400).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

161720 is a wasteful number, since it uses less digits than its factorization.

161720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 335 (or 331 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 161720 is about 402.1442527253. The cubic root of 161720 is about 54.4821926504.

Adding to 161720 its reverse (27161), we get a palindrome (188881).

The spelling of 161720 in words is "one hundred sixty-one thousand, seven hundred twenty".