128906981 has 4 divisors (see below), whose sum is σ = 147322272. Its totient is φ = 110491692.

The previous prime is 128906951. The next prime is 128907011. The reversal of 128906981 is 189609821.

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: 189609821 = 631 ⋅300491.

It is an interprime number because it is at equal distance from previous prime (128906951) and next prime (128907011).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128906981 is a prime.

It is a super-2 number, since 2×128906981² = 33234019501068722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128906941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9207635 + ... + 9207648.

It is an arithmetic number, because the mean of its divisors is an integer number (36830568).

Almost surely, 2^128906981 is an apocalyptic number.

It is an amenable number.

128906981 is a deficient number, since it is larger than the sum of its proper divisors (18415291).

128906981 is an equidigital number, since it uses as much as digits as its factorization.

128906981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18415290.

The product of its (nonzero) digits is 62208, while the sum is 44.

The square root of 128906981 is about 11353.7210200004. The cubic root of 128906981 is about 505.1559574516.

The spelling of 128906981 in words is "one hundred twenty-eight million, nine hundred six thousand, nine hundred eighty-one".