6561697219261 has 2 divisors, whose sum is σ = 6561697219262. Its totient is φ = 6561697219260.

The previous prime is 6561697219229. The next prime is 6561697219291. The reversal of 6561697219261 is 1629127961656.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3668316631225 + 2893380588036 = 1915285^2 + 1700994^2 .

It is a cyclic number.

It is not a de Polignac number, because 6561697219261 - 2⁵ = 6561697219229 is a prime.

It is a super-2 number, since 2×6561697219261² (a number of 26 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 6561697219261.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6561697219291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3280848609630 + 3280848609631.

It is an arithmetic number, because the mean of its divisors is an integer number (3280848609631).

Almost surely, 2^{6561697219261} is an apocalyptic number.

It is an amenable number.

6561697219261 is a deficient number, since it is larger than the sum of its proper divisors (1).

6561697219261 is an equidigital number, since it uses as much as digits as its factorization.

6561697219261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14696640, while the sum is 61.

The spelling of 6561697219261 in words is "six trillion, five hundred sixty-one billion, six hundred ninety-seven million, two hundred nineteen thousand, two hundred sixty-one".