6561661560 has 64 divisors (see below), whose sum is σ = 19722955680. Its totient is φ = 1746401280.

The previous prime is 6561661541. The next prime is 6561661591. The reversal of 6561661560 is 651661656.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10044 + ... + 114996.

Almost surely, 2^6561661560 is an apocalyptic number.

6561661560 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

6561661560 is an abundant number, since it is smaller than the sum of its proper divisors (13161294120).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6561661560 is a wasteful number, since it uses less digits than its factorization.

6561661560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105488 (or 105484 counting only the distinct ones).

The product of its (nonzero) digits is 194400, while the sum is 42.

The square root of 6561661560 is about 81004.0836007667. The cubic root of 6561661560 is about 1872.1383604543.

The spelling of 6561661560 in words is "six billion, five hundred sixty-one million, six hundred sixty-one thousand, five hundred sixty".