128625661 has 2 divisors, whose sum is σ = 128625662. Its totient is φ = 128625660.

The previous prime is 128625631. The next prime is 128625677. The reversal of 128625661 is 166526821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 127554436 + 1071225 = 11294^2 + 1035^2 .

It is a cyclic number.

It is not a de Polignac number, because 128625661 - 2¹⁷ = 128494589 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 128625661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128625631) 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 as a sum of consecutive naturals, namely, 64312830 + 64312831.

It is an arithmetic number, because the mean of its divisors is an integer number (64312831).

Almost surely, 2^128625661 is an apocalyptic number.

It is an amenable number.

128625661 is a deficient number, since it is larger than the sum of its proper divisors (1).

128625661 is an equidigital number, since it uses as much as digits as its factorization.

128625661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34560, while the sum is 37.

The square root of 128625661 is about 11341.3253634661. The cubic root of 128625661 is about 504.7882143018.

It can be divided in two parts, 128625 and 661, that added together give a triangular number (129286 = T₅₀₈).

The spelling of 128625661 in words is "one hundred twenty-eight million, six hundred twenty-five thousand, six hundred sixty-one".