128505780 has 72 divisors (see below), whose sum is σ = 419793192. Its totient is φ = 31631616.

The previous prime is 128505763. The next prime is 128505781. The reversal of 128505780 is 87505821.

128505780 is a `hidden beast` number, since 1 + 2 + 85 + 0 + 578 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 318096 + 128187684 = 564^2 + 11322^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128505781) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25119 + ... + 29798.

It is an arithmetic number, because the mean of its divisors is an integer number (5830461).

Almost surely, 2^128505780 is an apocalyptic number.

128505780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

128505780 is an abundant number, since it is smaller than the sum of its proper divisors (291287412).

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

128505780 is a wasteful number, since it uses less digits than its factorization.

128505780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54945 (or 54940 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The square root of 128505780 is about 11336.0389907586. The cubic root of 128505780 is about 504.6313422196.

The spelling of 128505780 in words is "one hundred twenty-eight million, five hundred five thousand, seven hundred eighty".