128720 has 20 divisors (see below), whose sum is σ = 299460. Its totient is φ = 51456.

The previous prime is 128717. The next prime is 128747. The reversal of 128720 is 27821.

128720 is nontrivially palindromic in base 9.

It can be written as a sum of positive squares in 2 ways, for example, as 94864 + 33856 = 308^2 + 184^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 128692 and 128701.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 725 + ... + 884.

It is an arithmetic number, because the mean of its divisors is an integer number (14973).

2¹²⁸⁷²⁰ is an apocalyptic number.

128720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

128720 is an abundant number, since it is smaller than the sum of its proper divisors (170740).

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

128720 is a wasteful number, since it uses less digits than its factorization.

128720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1622 (or 1616 counting only the distinct ones).

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

The square root of 128720 is about 358.7756959439. The cubic root of 128720 is about 50.4911594497.

It can be divided in two parts, 128 and 720, that added together give a palindrome (848).

The spelling of 128720 in words is "one hundred twenty-eight thousand, seven hundred twenty".