128731666 has 16 divisors (see below), whose sum is σ = 222827904. Its totient is φ = 54634464.

The previous prime is 128731661. The next prime is 128731693. The reversal of 128731666 is 666137821.

It is a happy number.

It is a super-2 number, since 2×128731666² = 33143683662271112, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (128731661) 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, 43195 + ... + 46078.

It is an arithmetic number, because the mean of its divisors is an integer number (13926744).

Almost surely, 2^128731666 is an apocalyptic number.

128731666 is a deficient number, since it is larger than the sum of its proper divisors (94096238).

128731666 is a wasteful number, since it uses less digits than its factorization.

128731666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89385.

The product of its digits is 72576, while the sum is 40.

The square root of 128731666 is about 11345.9977965801. The cubic root of 128731666 is about 504.9268475551.

The spelling of 128731666 in words is "one hundred twenty-eight million, seven hundred thirty-one thousand, six hundred sixty-six".