61515566561 has 4 divisors (see below), whose sum is σ = 61516132500. Its totient is φ = 61515000624.

The previous prime is 61515566537. The next prime is 61515566569. The reversal of 61515566561 is 16566551516.

61515566561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 20979784336 + 40535782225 = 144844^2 + 201335^2 .

It is a cyclic number.

It is not a de Polignac number, because 61515566561 - 2¹⁰ = 61515565537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61515566569) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62846 + ... + 356343.

It is an arithmetic number, because the mean of its divisors is an integer number (15379033125).

Almost surely, 2^61515566561 is an apocalyptic number.

It is an amenable number.

61515566561 is a deficient number, since it is larger than the sum of its proper divisors (565939).

61515566561 is a wasteful number, since it uses less digits than its factorization.

61515566561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 565938.

The product of its digits is 810000, while the sum is 47.

The spelling of 61515566561 in words is "sixty-one billion, five hundred fifteen million, five hundred sixty-six thousand, five hundred sixty-one".