1561681161 has 8 divisors (see below), whose sum is σ = 2313601760. Its totient is φ = 1041120756.

The previous prime is 1561681153. The next prime is 1561681169. The reversal of 1561681161 is 1611861651.

1561681161 is a `hidden beast` number, since 1 + 561 + 6 + 81 + 16 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (1561681153) and next prime (1561681169).

It is not a de Polignac number, because 1561681161 - 2³ = 1561681153 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1561681169) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28919995 + ... + 28920048.

It is an arithmetic number, because the mean of its divisors is an integer number (289200220).

Almost surely, 2^1561681161 is an apocalyptic number.

It is an amenable number.

1561681161 is a deficient number, since it is larger than the sum of its proper divisors (751920599).

1561681161 is an equidigital number, since it uses as much as digits as its factorization.

1561681161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57840052 (or 57840046 counting only the distinct ones).

The product of its digits is 8640, while the sum is 36.

The square root of 1561681161 is about 39518.1118096500. Note that the first 3 decimals coincide. The cubic root of 1561681161 is about 1160.1944682388.

The spelling of 1561681161 in words is "one billion, five hundred sixty-one million, six hundred eighty-one thousand, one hundred sixty-one".