128787221 has 4 divisors (see below), whose sum is σ = 130062444. Its totient is φ = 127512000.

The previous prime is 128787203. The next prime is 128787229. The reversal of 128787221 is 122787821.

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 85359121 + 43428100 = 9239^2 + 6590^2 .

It is a cyclic number.

It is not a de Polignac number, because 128787221 - 2¹⁰ = 128786197 is a prime.

It is a super-2 number, since 2×128787221² = 33172296585805682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128787229) 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, 637460 + ... + 637661.

It is an arithmetic number, because the mean of its divisors is an integer number (32515611).

Almost surely, 2^128787221 is an apocalyptic number.

It is an amenable number.

128787221 is a deficient number, since it is larger than the sum of its proper divisors (1275223).

128787221 is a wasteful number, since it uses less digits than its factorization.

128787221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1275222.

The product of its digits is 25088, while the sum is 38.

The square root of 128787221 is about 11348.4457526130. The cubic root of 128787221 is about 504.9994719466. Note that the first 3 decimals are identical.

The spelling of 128787221 in words is "one hundred twenty-eight million, seven hundred eighty-seven thousand, two hundred twenty-one".