1728561307805 has 4 divisors (see below), whose sum is σ = 2074273569372. Its totient is φ = 1382849046240.

The previous prime is 1728561307801. The next prime is 1728561307807. The reversal of 1728561307805 is 5087031658271.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1323875757604 + 404685550201 = 1150598^2 + 636149^2 .

It is not a de Polignac number, because 1728561307805 - 2² = 1728561307801 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1728561307801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 172856130776 + ... + 172856130785.

It is an arithmetic number, because the mean of its divisors is an integer number (518568392343).

Almost surely, 2^{1728561307805} is an apocalyptic number.

It is an amenable number.

1728561307805 is a deficient number, since it is larger than the sum of its proper divisors (345712261567).

1728561307805 is an equidigital number, since it uses as much as digits as its factorization.

1728561307805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345712261566.

The product of its (nonzero) digits is 2822400, while the sum is 53.

The spelling of 1728561307805 in words is "one trillion, seven hundred twenty-eight billion, five hundred sixty-one million, three hundred seven thousand, eight hundred five".