128921 has 8 divisors (see below), whose sum is σ = 142464. Its totient is φ = 115920.

The previous prime is 128903. The next prime is 128923. The reversal of 128921 is 129821.

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 128921 - 2⁶ = 128857 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 128921.

It is not an unprimeable number, because it can be changed into a prime (128923) 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, 506 + ... + 716.

It is an arithmetic number, because the mean of its divisors is an integer number (17808).

2¹²⁸⁹²¹ is an apocalyptic number.

It is an amenable number.

128921 is a deficient number, since it is larger than the sum of its proper divisors (13543).

128921 is a wasteful number, since it uses less digits than its factorization.

128921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271.

The product of its digits is 288, while the sum is 23.

The square root of 128921 is about 359.0557059845. The cubic root of 128921 is about 50.5174269169.

Subtracting 128921 from its reverse (129821), we obtain a square (900 = 30²).

The spelling of 128921 in words is "one hundred twenty-eight thousand, nine hundred twenty-one".