1565551116661 has 6 divisors (see below), whose sum is σ = 1821151299030. Its totient is φ = 1341900957096.

The previous prime is 1565551116599. The next prime is 1565551116671. The reversal of 1565551116661 is 1666111555651.

It can be written as a sum of positive squares in only one way, i.e., 1558976988100 + 6574128561 = 1248590^2 + 81081^2 .

It is not a de Polignac number, because 1565551116661 - 2²⁷ = 1565416898933 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49), and also a Moran number because the ratio is a prime number: 31950022789 = 1565551116661 / (1 + 5 + 6 + 5 + 5 + 5 + 1 + 1 + 1 + 6 + 6 + 6 + 1).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1565551116671) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 15975011346 + ... + 15975011443.

It is an arithmetic number, because the mean of its divisors is an integer number (303525216505).

Almost surely, 2^{1565551116661} is an apocalyptic number.

It is an amenable number.

1565551116661 is a deficient number, since it is larger than the sum of its proper divisors (255600182369).

1565551116661 is an equidigital number, since it uses as much as digits as its factorization.

1565551116661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31950022803 (or 31950022796 counting only the distinct ones).

The product of its digits is 810000, while the sum is 49.

The spelling of 1565551116661 in words is "one trillion, five hundred sixty-five billion, five hundred fifty-one million, one hundred sixteen thousand, six hundred sixty-one".