172820 has 12 divisors (see below), whose sum is σ = 362964. Its totient is φ = 69120.

The previous prime is 172807. The next prime is 172829. The reversal of 172820 is 28271.

It can be written as a sum of positive squares in 2 ways, for example, as 26896 + 145924 = 164^2 + 382^2 .

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 8641 = 172820 / (1 + 7 + 2 + 8 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 172792 and 172801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172829) by changing a digit.

172820 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4301 + ... + 4340.

It is an arithmetic number, because the mean of its divisors is an integer number (30247).

2¹⁷²⁸²⁰ is an apocalyptic number.

172820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

172820 is an abundant number, since it is smaller than the sum of its proper divisors (190144).

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

172820 is a wasteful number, since it uses less digits than its factorization.

172820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8650 (or 8648 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 20.

The square root of 172820 is about 415.7162493817. The cubic root of 172820 is about 55.7012148042.

The spelling of 172820 in words is "one hundred seventy-two thousand, eight hundred twenty".