128171781 has 16 divisors (see below), whose sum is σ = 194517120. Its totient is φ = 83363040.

The previous prime is 128171779. The next prime is 128171783. The reversal of 128171781 is 187171821.

It is an interprime number because it is at equal distance from previous prime (128171779) and next prime (128171783).

It is not a de Polignac number, because 128171781 - 2¹ = 128171779 is a prime.

It is a super-2 number, since 2×128171781² = 32856010889423922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128171783) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56785 + ... + 58998.

It is an arithmetic number, because the mean of its divisors is an integer number (12157320).

Almost surely, 2^128171781 is an apocalyptic number.

It is an amenable number.

128171781 is a deficient number, since it is larger than the sum of its proper divisors (66345339).

128171781 is a wasteful number, since it uses less digits than its factorization.

128171781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115833 (or 115827 counting only the distinct ones).

The product of its digits is 6272, while the sum is 36.

The square root of 128171781 is about 11321.2976729702. The cubic root of 128171781 is about 504.1937676148.

The spelling of 128171781 in words is "one hundred twenty-eight million, one hundred seventy-one thousand, seven hundred eighty-one".