128721056 has 24 divisors (see below), whose sum is σ = 256272660. Its totient is φ = 63635968.

The previous prime is 128721013. The next prime is 128721071. The reversal of 128721056 is 650127821.

It can be written as a sum of positive squares in 2 ways, for example, as 127328656 + 1392400 = 11284^2 + 1180^2 .

It is a super-2 number, since 2×128721056² = 33138220515510272, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (32).

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, 19751 + ... + 25446.

Almost surely, 2^128721056 is an apocalyptic number.

128721056 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

128721056 is a deficient number, since it is larger than the sum of its proper divisors (127551604).

128721056 is an equidigital number, since it uses as much as digits as its factorization.

128721056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45296 (or 45288 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 32.

The square root of 128721056 is about 11345.5302211928. The cubic root of 128721056 is about 504.9129752339.

Adding to 128721056 its reverse (650127821), we get a palindrome (778848877).

It can be divided in two parts, 1287 and 21056, that multiplied together give a palindrome (27099072).

The spelling of 128721056 in words is "one hundred twenty-eight million, seven hundred twenty-one thousand, fifty-six".