1665981668 has 24 divisors (see below), whose sum is σ = 3170831160. Its totient is φ = 761299200.

The previous prime is 1665981619. The next prime is 1665981673. The reversal of 1665981668 is 8661895661.

It can be written as a sum of positive squares in 4 ways, for example, as 336795904 + 1329185764 = 18352^2 + 36458^2 .

It is a super-2 number, since 2×1665981668² = 5550989836224124448, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 153353 + ... + 163856.

It is an arithmetic number, because the mean of its divisors is an integer number (132117965).

Almost surely, 2^1665981668 is an apocalyptic number.

It is an amenable number.

1665981668 is a deficient number, since it is larger than the sum of its proper divisors (1504849492).

1665981668 is a wasteful number, since it uses less digits than its factorization.

1665981668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317327 (or 317325 counting only the distinct ones).

The product of its digits is 3732480, while the sum is 56.

The square root of 1665981668 is about 40816.4386981520. The cubic root of 1665981668 is about 1185.4686480938.

The spelling of 1665981668 in words is "one billion, six hundred sixty-five million, nine hundred eighty-one thousand, six hundred sixty-eight".