128009821 has 8 divisors (see below), whose sum is σ = 136372320. Its totient is φ = 119809872.

The previous prime is 128009809. The next prime is 128009851. The reversal of 128009821 is 128900821.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 128009821 - 2¹⁵ = 127977053 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128009851) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39010 + ... + 42163.

It is an arithmetic number, because the mean of its divisors is an integer number (17046540).

Almost surely, 2^128009821 is an apocalyptic number.

It is an amenable number.

128009821 is a deficient number, since it is larger than the sum of its proper divisors (8362499).

128009821 is an equidigital number, since it uses as much as digits as its factorization.

128009821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81275.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 128009821 is about 11314.1425216408. The cubic root of 128009821 is about 503.9813088831.

The spelling of 128009821 in words is "one hundred twenty-eight million, nine thousand, eight hundred twenty-one".