128667661 has 2 divisors, whose sum is σ = 128667662. Its totient is φ = 128667660.

The previous prime is 128667647. The next prime is 128667689. The reversal of 128667661 is 166766821.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 119486761 + 9180900 = 10931^2 + 3030^2 .

It is a cyclic number.

It is not a de Polignac number, because 128667661 - 2⁷ = 128667533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128667641) 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, 64333830 + 64333831.

It is an arithmetic number, because the mean of its divisors is an integer number (64333831).

Almost surely, 2^128667661 is an apocalyptic number.

It is an amenable number.

128667661 is a deficient number, since it is larger than the sum of its proper divisors (1).

128667661 is an equidigital number, since it uses as much as digits as its factorization.

128667661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145152, while the sum is 43.

The square root of 128667661 is about 11343.1768477795. The cubic root of 128667661 is about 504.8431509753.

The spelling of 128667661 in words is "one hundred twenty-eight million, six hundred sixty-seven thousand, six hundred sixty-one".