128111661 has 24 divisors (see below), whose sum is σ = 195829920. Its totient is φ = 80480736.

The previous prime is 128111639. The next prime is 128111689. The reversal of 128111661 is 166111821.

It is not a de Polignac number, because 128111661 - 2¹⁰ = 128110637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128111611) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 31786 + ... + 35588.

It is an arithmetic number, because the mean of its divisors is an integer number (8159580).

Almost surely, 2^128111661 is an apocalyptic number.

It is an amenable number.

128111661 is a deficient number, since it is larger than the sum of its proper divisors (67718259).

128111661 is a wasteful number, since it uses less digits than its factorization.

128111661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4025 (or 4022 counting only the distinct ones).

The product of its digits is 576, while the sum is 27.

The square root of 128111661 is about 11318.6421888847. The cubic root of 128111661 is about 504.1149232449.

The spelling of 128111661 in words is "one hundred twenty-eight million, one hundred eleven thousand, six hundred sixty-one".