6561551657 has 2 divisors, whose sum is σ = 6561551658. Its totient is φ = 6561551656.

The previous prime is 6561551653. The next prime is 6561551671. The reversal of 6561551657 is 7561551656.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5016747241 + 1544804416 = 70829^2 + 39304^2 .

It is a cyclic number.

It is not a de Polignac number, because 6561551657 - 2² = 6561551653 is a prime.

It is not a weakly prime, because it can be changed into another prime (6561551651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3280775828 + 3280775829.

It is an arithmetic number, because the mean of its divisors is an integer number (3280775829).

Almost surely, 2^6561551657 is an apocalyptic number.

It is an amenable number.

6561551657 is a deficient number, since it is larger than the sum of its proper divisors (1).

6561551657 is an equidigital number, since it uses as much as digits as its factorization.

6561551657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 945000, while the sum is 47.

The square root of 6561551657 is about 81003.4052185462. The cubic root of 6561551657 is about 1872.1279080829.

Subtracting 6561551657 from its reverse (7561551656), we obtain a palindrome (999999999).

The spelling of 6561551657 in words is "six billion, five hundred sixty-one million, five hundred fifty-one thousand, six hundred fifty-seven".