128856661 has 2 divisors, whose sum is σ = 128856662. Its totient is φ = 128856660.

The previous prime is 128856659. The next prime is 128856671. The reversal of 128856661 is 166658821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 124880625 + 3976036 = 11175^2 + 1994^2 .

It is a cyclic number.

It is not a de Polignac number, because 128856661 - 2¹ = 128856659 is a prime.

Together with 128856659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128856601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64428330 + 64428331.

It is an arithmetic number, because the mean of its divisors is an integer number (64428331).

Almost surely, 2^128856661 is an apocalyptic number.

It is an amenable number.

128856661 is a deficient number, since it is larger than the sum of its proper divisors (1).

128856661 is an equidigital number, since it uses as much as digits as its factorization.

128856661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 138240, while the sum is 43.

The square root of 128856661 is about 11351.5047901148. The cubic root of 128856661 is about 505.0902181723.

The spelling of 128856661 in words is "one hundred twenty-eight million, eight hundred fifty-six thousand, six hundred sixty-one".