128707821 has 18 divisors (see below), whose sum is σ = 204350510. Its totient is φ = 78004080.

The previous prime is 128707811. The next prime is 128707823.

It is a happy number.

128707821 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in only one way, i.e., 127373796 + 1334025 = 11286^2 + 1155^2 .

It is not a de Polignac number, because 128707821 - 2⁷ = 128707693 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128707823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 58006 + ... + 60183.

Almost surely, 2^128707821 is an apocalyptic number.

128707821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

128707821 is a deficient number, since it is larger than the sum of its proper divisors (75642689).

128707821 is a wasteful number, since it uses less digits than its factorization.

128707821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118217 (or 118203 counting only the distinct ones).

The product of its (nonzero) digits is 12544, while the sum is 36.

The square root of 128707821 is about 11344.9469368525. The cubic root of 128707821 is about 504.8956697195.

The spelling of 128707821 in words is "one hundred twenty-eight million, seven hundred seven thousand, eight hundred twenty-one".