1668721871 has 4 divisors (see below), whose sum is σ = 1669116672. Its totient is φ = 1668327072.

The previous prime is 1668721823. The next prime is 1668721877. The reversal of 1668721871 is 1781278661.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1668721871 - 2¹⁴ = 1668705487 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 (1668721877) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 190991 + ... + 199536.

It is an arithmetic number, because the mean of its divisors is an integer number (417279168).

Almost surely, 2^1668721871 is an apocalyptic number.

1668721871 is a deficient number, since it is larger than the sum of its proper divisors (394801).

1668721871 is an equidigital number, since it uses as much as digits as its factorization.

1668721871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394800.

The product of its digits is 225792, while the sum is 47.

The square root of 1668721871 is about 40849.9923011009. The cubic root of 1668721871 is about 1186.1182441515.

The spelling of 1668721871 in words is "one billion, six hundred sixty-eight million, seven hundred twenty-one thousand, eight hundred seventy-one".