6561578549 has 2 divisors, whose sum is σ = 6561578550. Its totient is φ = 6561578548.

The previous prime is 6561578531. The next prime is 6561578561. The reversal of 6561578549 is 9458751656.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6252064900 + 309513649 = 79070^2 + 17593^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6561578549 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 6561578494 and 6561578503.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6561578509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3280789274 + 3280789275.

It is an arithmetic number, because the mean of its divisors is an integer number (3280789275).

Almost surely, 2^6561578549 is an apocalyptic number.

It is an amenable number.

6561578549 is a deficient number, since it is larger than the sum of its proper divisors (1).

6561578549 is an equidigital number, since it uses as much as digits as its factorization.

6561578549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072000, while the sum is 56.

The square root of 6561578549 is about 81003.5712113978. The cubic root of 6561578549 is about 1872.1304656687.

The spelling of 6561578549 in words is "six billion, five hundred sixty-one million, five hundred seventy-eight thousand, five hundred forty-nine".