561661011561 has 16 divisors (see below), whose sum is σ = 853928054784. Its totient is φ = 325305924864.

The previous prime is 561661011559. The next prime is 561661011577. The reversal of 561661011561 is 165110166165.

It is not a de Polignac number, because 561661011561 - 2¹ = 561661011559 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (561661011521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 423574761 + ... + 423576086.

It is an arithmetic number, because the mean of its divisors is an integer number (53370503424).

Almost surely, 2^561661011561 is an apocalyptic number.

561661011561 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

It is an amenable number.

561661011561 is a deficient number, since it is larger than the sum of its proper divisors (292267043223).

561661011561 is a wasteful number, since it uses less digits than its factorization.

561661011561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 847150880.

The product of its (nonzero) digits is 32400, while the sum is 39.

The spelling of 561661011561 in words is "five hundred sixty-one billion, six hundred sixty-one million, eleven thousand, five hundred sixty-one".