128921821 has 16 divisors (see below), whose sum is σ = 156534400. Its totient is φ = 103716288.

The previous prime is 128921809. The next prime is 128921851. The reversal of 128921821 is 128129821.

It is not a de Polignac number, because 128921821 - 2¹⁷ = 128790749 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 (128921851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10051 + ... + 18943.

It is an arithmetic number, because the mean of its divisors is an integer number (9783400).

Almost surely, 2^128921821 is an apocalyptic number.

It is an amenable number.

128921821 is a deficient number, since it is larger than the sum of its proper divisors (27612579).

128921821 is a wasteful number, since it uses less digits than its factorization.

128921821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9028.

The product of its digits is 4608, while the sum is 34.

The square root of 128921821 is about 11354.3745314306. The cubic root of 128921821 is about 505.1753415240.

The spelling of 128921821 in words is "one hundred twenty-eight million, nine hundred twenty-one thousand, eight hundred twenty-one".