1668608991 has 40 divisors (see below), whose sum is σ = 2972580864. Its totient is φ = 912027600.

The previous prime is 1668608987. The next prime is 1668609029. The reversal of 1668608991 is 1998068661.

It is not a de Polignac number, because 1668608991 - 2² = 1668608987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1668608891) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 50935 + ... + 77016.

Almost surely, 2^1668608991 is an apocalyptic number.

1668608991 is a deficient number, since it is larger than the sum of its proper divisors (1303971873).

1668608991 is a wasteful number, since it uses less digits than its factorization.

1668608991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127993 (or 127984 counting only the distinct ones).

The product of its (nonzero) digits is 1119744, while the sum is 54.

The square root of 1668608991 is about 40848.6106373277. The cubic root of 1668608991 is about 1186.0914987226.

The spelling of 1668608991 in words is "one billion, six hundred sixty-eight million, six hundred eight thousand, nine hundred ninety-one".