1661220831577 has 4 divisors (see below), whose sum is σ = 1664631963136. Its totient is φ = 1657809700020.

The previous prime is 1661220831563. The next prime is 1661220831601. The reversal of 1661220831577 is 7751380221661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1661220831577 - 2¹¹ = 1661220829529 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661220831577.

It is not an unprimeable number, because it can be changed into a prime (1661220831377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1705565049 + ... + 1705566022.

It is an arithmetic number, because the mean of its divisors is an integer number (416157990784).

Almost surely, 2^{1661220831577} is an apocalyptic number.

It is an amenable number.

1661220831577 is a deficient number, since it is larger than the sum of its proper divisors (3411131559).

1661220831577 is an equidigital number, since it uses as much as digits as its factorization.

1661220831577 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3411131558.

The product of its (nonzero) digits is 846720, while the sum is 49.

The spelling of 1661220831577 in words is "one trillion, six hundred sixty-one billion, two hundred twenty million, eight hundred thirty-one thousand, five hundred seventy-seven".