128661 has 8 divisors (see below), whose sum is σ = 184800. Its totient is φ = 79152.

The previous prime is 128659. The next prime is 128663. The reversal of 128661 is 166821.

It is an interprime number because it is at equal distance from previous prime (128659) and next prime (128663).

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

It is not a de Polignac number, because 128661 - 2¹ = 128659 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1611 + ... + 1688.

It is an arithmetic number, because the mean of its divisors is an integer number (23100).

2¹²⁸⁶⁶¹ is an apocalyptic number.

It is an amenable number.

128661 is a deficient number, since it is larger than the sum of its proper divisors (56139).

128661 is a wasteful number, since it uses less digits than its factorization.

128661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3315.

The product of its digits is 576, while the sum is 24.

The square root of 128661 is about 358.6934624439. The cubic root of 128661 is about 50.4834439078.

The spelling of 128661 in words is "one hundred twenty-eight thousand, six hundred sixty-one".