128728751 has 4 divisors (see below), whose sum is σ = 130541904. Its totient is φ = 126915600.

The previous prime is 128728741. The next prime is 128728753. The reversal of 128728751 is 157827821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 157827821 = 7753 ⋅20357.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128728751 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 128728699 and 128728708.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128728753) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 906470 + ... + 906611.

It is an arithmetic number, because the mean of its divisors is an integer number (32635476).

Almost surely, 2^128728751 is an apocalyptic number.

128728751 is a deficient number, since it is larger than the sum of its proper divisors (1813153).

128728751 is an equidigital number, since it uses as much as digits as its factorization.

128728751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1813152.

The product of its digits is 62720, while the sum is 41.

The square root of 128728751 is about 11345.8693364590. The cubic root of 128728751 is about 504.9230363383.

The spelling of 128728751 in words is "one hundred twenty-eight million, seven hundred twenty-eight thousand, seven hundred fifty-one".