1661223304645 has 4 divisors (see below), whose sum is σ = 1993467965580. Its totient is φ = 1328978643712.

The previous prime is 1661223304537. The next prime is 1661223304703. The reversal of 1661223304645 is 5464033221661.

It is a happy number.

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 891859250689 + 769364053956 = 944383^2 + 877134^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661223304645 - 2²³ = 1661214916037 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166122330460 + ... + 166122330469.

It is an arithmetic number, because the mean of its divisors is an integer number (498366991395).

Almost surely, 2^{1661223304645} is an apocalyptic number.

It is an amenable number.

1661223304645 is a deficient number, since it is larger than the sum of its proper divisors (332244660935).

1661223304645 is an equidigital number, since it uses as much as digits as its factorization.

1661223304645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332244660934.

The product of its (nonzero) digits is 622080, while the sum is 43.

The spelling of 1661223304645 in words is "one trillion, six hundred sixty-one billion, two hundred twenty-three million, three hundred four thousand, six hundred forty-five".