1668778057 has 4 divisors (see below), whose sum is σ = 1668869316. Its totient is φ = 1668686800.

The previous prime is 1668778043. The next prime is 1668778079. The reversal of 1668778057 is 7508778661.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 7508778661 = 151 ⋅49727011.

It can be written as a sum of positive squares in 2 ways, for example, as 985269321 + 683508736 = 31389^2 + 26144^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1668778057 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1668777989 and 1668778007.

It is not an unprimeable number, because it can be changed into a prime (1668778457) 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, 7678 + ... + 58279.

It is an arithmetic number, because the mean of its divisors is an integer number (417217329).

Almost surely, 2^1668778057 is an apocalyptic number.

It is an amenable number.

1668778057 is a deficient number, since it is larger than the sum of its proper divisors (91259).

1668778057 is an equidigital number, since it uses as much as digits as its factorization.

1668778057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91258.

The product of its (nonzero) digits is 3951360, while the sum is 55.

The square root of 1668778057 is about 40850.6800065801. The cubic root of 1668778057 is about 1186.1315562344.

The spelling of 1668778057 in words is "one billion, six hundred sixty-eight million, seven hundred seventy-eight thousand, fifty-seven".