128656720 has 20 divisors (see below), whose sum is σ = 299127060. Its totient is φ = 51462656.

The previous prime is 128656711. The next prime is 128656751. The reversal of 128656720 is 27656821.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 72046144 + 56610576 = 8488^2 + 7524^2 .

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

It is a super-3 number, since 3×128656720³ (a number of 25 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 128656720.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 804025 + ... + 804184.

It is an arithmetic number, because the mean of its divisors is an integer number (14956353).

Almost surely, 2^128656720 is an apocalyptic number.

128656720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

128656720 is an abundant number, since it is smaller than the sum of its proper divisors (170470340).

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

128656720 is a wasteful number, since it uses less digits than its factorization.

128656720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1608222 (or 1608216 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 37.

The square root of 128656720 is about 11342.6945652257. The cubic root of 128656720 is about 504.8288411235.

The spelling of 128656720 in words is "one hundred twenty-eight million, six hundred fifty-six thousand, seven hundred twenty".