6561521077 has 2 divisors, whose sum is σ = 6561521078. Its totient is φ = 6561521076.

The previous prime is 6561521027. The next prime is 6561521111. The reversal of 6561521077 is 7701251656.

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., 6131829636 + 429691441 = 78306^2 + 20729^2 .

It is a cyclic number.

It is not a de Polignac number, because 6561521077 - 2¹⁵ = 6561488309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6561521027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3280760538 + 3280760539.

It is an arithmetic number, because the mean of its divisors is an integer number (3280760539).

Almost surely, 2^6561521077 is an apocalyptic number.

It is an amenable number.

6561521077 is a deficient number, since it is larger than the sum of its proper divisors (1).

6561521077 is an equidigital number, since it uses as much as digits as its factorization.

6561521077 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 88200, while the sum is 40.

The square root of 6561521077 is about 81003.2164608295. The cubic root of 6561521077 is about 1872.1249997383.

The spelling of 6561521077 in words is "six billion, five hundred sixty-one million, five hundred twenty-one thousand, seventy-seven".