1668978261 has 12 divisors (see below), whose sum is σ = 2420752620. Its totient is φ = 1108033920.

The previous prime is 1668978209. The next prime is 1668978271. The reversal of 1668978261 is 1628798661.

It can be written as a sum of positive squares in 2 ways, for example, as 1492354161 + 176624100 = 38631^2 + 13290^2 .

It is not a de Polignac number, because 1668978261 - 2⁷ = 1668978133 is a prime.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 1668978198 and 1668978207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1668978271) 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 11 ways as a sum of consecutive naturals, for example, 382566 + ... + 386903.

It is an arithmetic number, because the mean of its divisors is an integer number (201729385).

Almost surely, 2^1668978261 is an apocalyptic number.

It is an amenable number.

1668978261 is a deficient number, since it is larger than the sum of its proper divisors (751774359).

1668978261 is a wasteful number, since it uses less digits than its factorization.

1668978261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 769716 (or 769713 counting only the distinct ones).

The product of its digits is 1741824, while the sum is 54.

The square root of 1668978261 is about 40853.1303696547. The cubic root of 1668978261 is about 1186.1789879036.

The spelling of 1668978261 in words is "one billion, six hundred sixty-eight million, nine hundred seventy-eight thousand, two hundred sixty-one".