128291681 has 4 divisors (see below), whose sum is σ = 146619072. Its totient is φ = 109964292.

The previous prime is 128291599. The next prime is 128291699. The reversal of 128291681 is 186192821.

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: 186192821 = 83 ⋅2243287.

It is a cyclic number.

It is not a de Polignac number, because 128291681 - 2¹⁴ = 128275297 is a prime.

It is a super-2 number, since 2×128291681² = 32917510827611522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (128296681) 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, 9163685 + ... + 9163698.

It is an arithmetic number, because the mean of its divisors is an integer number (36654768).

Almost surely, 2^128291681 is an apocalyptic number.

It is an amenable number.

128291681 is a deficient number, since it is larger than the sum of its proper divisors (18327391).

128291681 is an equidigital number, since it uses as much as digits as its factorization.

128291681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18327390.

The product of its digits is 13824, while the sum is 38.

The square root of 128291681 is about 11326.5917645159. The cubic root of 128291681 is about 504.3509368752.

The spelling of 128291681 in words is "one hundred twenty-eight million, two hundred ninety-one thousand, six hundred eighty-one".