128821 has 12 divisors (see below), whose sum is σ = 164160. Its totient is φ = 99960.

The previous prime is 128819. The next prime is 128831.

128821 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 128821 - 2¹ = 128819 is a prime.

It is a Duffinian number.

128821 is a lucky number.

It is a nialpdrome in base 11.

It is a junction number, because it is equal to n+sod(n) for n = 128792 and 128801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128831) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 420 + ... + 658.

It is an arithmetic number, because the mean of its divisors is an integer number (13680).

2¹²⁸⁸²¹ is an apocalyptic number.

128821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

128821 is a deficient number, since it is larger than the sum of its proper divisors (35339).

128821 is a wasteful number, since it uses less digits than its factorization.

128821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264 (or 257 counting only the distinct ones).

The product of its digits is 256, while the sum is 22.

The square root of 128821 is about 358.9164248122. The cubic root of 128821 is about 50.5043619406.

It can be divided in two parts, 128 and 821, that added together give a palindrome (949).

The spelling of 128821 in words is "one hundred twenty-eight thousand, eight hundred twenty-one".