128820421 has 4 divisors (see below), whose sum is σ = 132302092. Its totient is φ = 125338752.

The previous prime is 128820409. The next prime is 128820427. The reversal of 128820421 is 124028821.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 63776196 + 65044225 = 7986^2 + 8065^2 .

It is a cyclic number.

It is not a de Polignac number, because 128820421 - 2¹⁷ = 128689349 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 128820421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128820427) 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, 1740780 + ... + 1740853.

It is an arithmetic number, because the mean of its divisors is an integer number (33075523).

Almost surely, 2^128820421 is an apocalyptic number.

It is an amenable number.

128820421 is a deficient number, since it is larger than the sum of its proper divisors (3481671).

128820421 is an equidigital number, since it uses as much as digits as its factorization.

128820421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3481670.

The product of its (nonzero) digits is 2048, while the sum is 28.

The square root of 128820421 is about 11349.9084137274. The cubic root of 128820421 is about 505.0428627475.

It can be divided in two parts, 1288204 and 21, that added together give a square (1288225 = 1135²).

The spelling of 128820421 in words is "one hundred twenty-eight million, eight hundred twenty thousand, four hundred twenty-one".