128666913 has 4 divisors (see below), whose sum is σ = 171555888. Its totient is φ = 85777940.

The previous prime is 128666893. The next prime is 128666921. The reversal of 128666913 is 319666821.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 319666821 = 3 ⋅106555607.

It is a cyclic number.

It is not a de Polignac number, because 128666913 - 2¹⁸ = 128404769 is a prime.

It is not an unprimeable number, because it can be changed into a prime (128666933) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21444483 + ... + 21444488.

It is an arithmetic number, because the mean of its divisors is an integer number (42888972).

Almost surely, 2^128666913 is an apocalyptic number.

It is an amenable number.

128666913 is a deficient number, since it is larger than the sum of its proper divisors (42888975).

128666913 is an equidigital number, since it uses as much as digits as its factorization.

128666913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42888974.

The product of its digits is 93312, while the sum is 42.

The square root of 128666913 is about 11343.1438763687. The cubic root of 128666913 is about 504.8421726839.

The spelling of 128666913 in words is "one hundred twenty-eight million, six hundred sixty-six thousand, nine hundred thirteen".