121556656577 has 2 divisors, whose sum is σ = 121556656578. Its totient is φ = 121556656576.

The previous prime is 121556656519. The next prime is 121556656583. The reversal of 121556656577 is 775656655121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 121353992881 + 202663696 = 348359^2 + 14236^2 .

It is an emirp because it is prime and its reverse (775656655121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 121556656577 - 2⁸ = 121556656321 is a prime.

It is not a weakly prime, because it can be changed into another prime (121556686577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 60778328288 + 60778328289.

It is an arithmetic number, because the mean of its divisors is an integer number (60778328289).

Almost surely, 2^121556656577 is an apocalyptic number.

It is an amenable number.

121556656577 is a deficient number, since it is larger than the sum of its proper divisors (1).

121556656577 is an equidigital number, since it uses as much as digits as its factorization.

121556656577 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13230000, while the sum is 56.

The spelling of 121556656577 in words is "one hundred twenty-one billion, five hundred fifty-six million, six hundred fifty-six thousand, five hundred seventy-seven".