128637661 has 2 divisors, whose sum is σ = 128637662. Its totient is φ = 128637660.

The previous prime is 128637653. The next prime is 128637671. The reversal of 128637661 is 166736821.

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., 116769636 + 11868025 = 10806^2 + 3445^2 .

It is a cyclic number.

It is not a de Polignac number, because 128637661 - 2³ = 128637653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128637671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64318830 + 64318831.

It is an arithmetic number, because the mean of its divisors is an integer number (64318831).

Almost surely, 2^128637661 is an apocalyptic number.

It is an amenable number.

128637661 is a deficient number, since it is larger than the sum of its proper divisors (1).

128637661 is an equidigital number, since it uses as much as digits as its factorization.

128637661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 128637661 is about 11341.8543898253. The cubic root of 128637661 is about 504.8039117144.

The spelling of 128637661 in words is "one hundred twenty-eight million, six hundred thirty-seven thousand, six hundred sixty-one".