61605555561 has 64 divisors (see below), whose sum is σ = 100961280000. Its totient is φ = 36814227840.

The previous prime is 61605555509. The next prime is 61605555563. The reversal of 61605555561 is 16555550616.

It is not a de Polignac number, because 61605555561 - 2³¹ = 59458071913 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (61605555563) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 24611436 + ... + 24613938.

It is an arithmetic number, because the mean of its divisors is an integer number (1577520000).

Almost surely, 2^61605555561 is an apocalyptic number.

It is an amenable number.

61605555561 is a deficient number, since it is larger than the sum of its proper divisors (39355724439).

61605555561 is a wasteful number, since it uses less digits than its factorization.

61605555561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3651 (or 3645 counting only the distinct ones).

The product of its (nonzero) digits is 675000, while the sum is 45.

The spelling of 61605555561 in words is "sixty-one billion, six hundred five million, five hundred fifty-five thousand, five hundred sixty-one".