128976781 has 2 divisors, whose sum is σ = 128976782. Its totient is φ = 128976780.

The previous prime is 128976763. The next prime is 128976787. The reversal of 128976781 is 187679821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69455556 + 59521225 = 8334^2 + 7715^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128976781 is a prime.

It is a super-2 number, since 2×128976781² = 33270020074243922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128976787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64488390 + 64488391.

It is an arithmetic number, because the mean of its divisors is an integer number (64488391).

Almost surely, 2^128976781 is an apocalyptic number.

It is an amenable number.

128976781 is a deficient number, since it is larger than the sum of its proper divisors (1).

128976781 is an equidigital number, since it uses as much as digits as its factorization.

128976781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 338688, while the sum is 49.

The square root of 128976781 is about 11356.7944861215. The cubic root of 128976781 is about 505.2471175614.

The spelling of 128976781 in words is "one hundred twenty-eight million, nine hundred seventy-six thousand, seven hundred eighty-one".