1668320257661 has 4 divisors (see below), whose sum is σ = 1707118403232. Its totient is φ = 1629522112092.

The previous prime is 1668320257657. The next prime is 1668320257693. The reversal of 1668320257661 is 1667520238661.

It is a happy number.

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 1668320257661 - 2² = 1668320257657 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 (1668320257621) by changing a digit.

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, 19399072721 + ... + 19399072806.

It is an arithmetic number, because the mean of its divisors is an integer number (426779600808).

Almost surely, 2^{1668320257661} is an apocalyptic number.

It is an amenable number.

1668320257661 is a deficient number, since it is larger than the sum of its proper divisors (38798145571).

1668320257661 is an equidigital number, since it uses as much as digits as its factorization.

1668320257661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38798145570.

The product of its (nonzero) digits is 4354560, while the sum is 53.

The spelling of 1668320257661 in words is "one trillion, six hundred sixty-eight billion, three hundred twenty million, two hundred fifty-seven thousand, six hundred sixty-one".