128640 has 64 divisors (see below), whose sum is σ = 416160. Its totient is φ = 33792.

The previous prime is 128629. The next prime is 128657. The reversal of 128640 is 46821.

It is a tau number, because it is divible by the number of its divisors (64).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1887 + ... + 1953.

2¹²⁸⁶⁴⁰ is an apocalyptic number.

128640 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 128640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (208080).

128640 is an abundant number, since it is smaller than the sum of its proper divisors (287520).

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

128640 is an equidigital number, since it uses as much as digits as its factorization.

128640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89 (or 77 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 128640 is about 358.6641883434. The cubic root of 128640 is about 50.4806971288.

It can be divided in two parts, 1286 and 40, that added together give a triangular number (1326 = T₅₁).

The spelling of 128640 in words is "one hundred twenty-eight thousand, six hundred forty".