1668991739 has 2 divisors, whose sum is σ = 1668991740. Its totient is φ = 1668991738.

The previous prime is 1668991729. The next prime is 1668991799. The reversal of 1668991739 is 9371998661.

It is a weak prime.

It is an emirp because it is prime and its reverse (9371998661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1668991739 - 2¹² = 1668987643 is a prime.

It is not a weakly prime, because it can be changed into another prime (1668991729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834495869 + 834495870.

It is an arithmetic number, because the mean of its divisors is an integer number (834495870).

Almost surely, 2^1668991739 is an apocalyptic number.

1668991739 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668991739 is an equidigital number, since it uses as much as digits as its factorization.

1668991739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4408992, while the sum is 59.

The square root of 1668991739 is about 40853.2953260811. The cubic root of 1668991739 is about 1186.1821809305.

The spelling of 1668991739 in words is "one billion, six hundred sixty-eight million, nine hundred ninety-one thousand, seven hundred thirty-nine".