1561565051661 has 16 divisors (see below), whose sum is σ = 2107310091264. Its totient is φ = 1028433332784.

The previous prime is 1561565051609. The next prime is 1561565051671. The reversal of 1561565051661 is 1661505651651.

It is not a de Polignac number, because 1561565051661 - 2⁷ = 1561565051533 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1561565051661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561565051671) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3758490 + ... + 4153236.

It is an arithmetic number, because the mean of its divisors is an integer number (131706880704).

Almost surely, 2^{1561565051661} is an apocalyptic number.

It is an amenable number.

1561565051661 is a deficient number, since it is larger than the sum of its proper divisors (545745039603).

1561565051661 is a wasteful number, since it uses less digits than its factorization.

1561565051661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410720.

The product of its (nonzero) digits is 810000, while the sum is 48.

The spelling of 1561565051661 in words is "one trillion, five hundred sixty-one billion, five hundred sixty-five million, fifty-one thousand, six hundred sixty-one".