2531661561 has 80 divisors (see below), whose sum is σ = 4480616448. Its totient is φ = 1404345600.

The previous prime is 2531661557. The next prime is 2531661599. The reversal of 2531661561 is 1651661352.

2531661561 is a `hidden beast` number, since 2 + 5 + 31 + 6 + 61 + 561 = 666.

It is not a de Polignac number, because 2531661561 - 2² = 2531661557 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2531661521) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 1470181 + ... + 1471901.

Almost surely, 2^2531661561 is an apocalyptic number.

It is an amenable number.

2531661561 is a deficient number, since it is larger than the sum of its proper divisors (1948954887).

2531661561 is a wasteful number, since it uses less digits than its factorization.

2531661561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1884 (or 1875 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 2531661561 is about 50315.6194536051. The cubic root of 2531661561 is about 1362.9143029392.

The spelling of 2531661561 in words is "two billion, five hundred thirty-one million, six hundred sixty-one thousand, five hundred sixty-one".