128856221 has 4 divisors (see below), whose sum is σ = 138768252. Its totient is φ = 118944192.

The previous prime is 128856199. The next prime is 128856263. The reversal of 128856221 is 122658821.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 122658821 = 89 ⋅1378189.

It can be written as a sum of positive squares in 2 ways, for example, as 62188996 + 66667225 = 7886^2 + 8165^2 .

It is a cyclic number.

It is not a de Polignac number, because 128856221 - 2¹⁰ = 128855197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128852221) 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, 4955996 + ... + 4956021.

It is an arithmetic number, because the mean of its divisors is an integer number (34692063).

Almost surely, 2^128856221 is an apocalyptic number.

It is an amenable number.

128856221 is a deficient number, since it is larger than the sum of its proper divisors (9912031).

128856221 is an equidigital number, since it uses as much as digits as its factorization.

128856221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9912030.

The product of its digits is 15360, while the sum is 35.

The square root of 128856221 is about 11351.4854094079. The cubic root of 128856221 is about 505.0896432701.

The spelling of 128856221 in words is "one hundred twenty-eight million, eight hundred fifty-six thousand, two hundred twenty-one".