1668781669 has 2 divisors, whose sum is σ = 1668781670. Its totient is φ = 1668781668.

The previous prime is 1668781661. The next prime is 1668781717. The reversal of 1668781669 is 9661878661.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1218917569 + 449864100 = 34913^2 + 21210^2 .

It is a cyclic number.

It is not a de Polignac number, because 1668781669 - 2³ = 1668781661 is a prime.

It is a super-2 number, since 2×1668781669² = 5569664517580851122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1668781661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 834390834 + 834390835.

It is an arithmetic number, because the mean of its divisors is an integer number (834390835).

Almost surely, 2^1668781669 is an apocalyptic number.

It is an amenable number.

1668781669 is a deficient number, since it is larger than the sum of its proper divisors (1).

1668781669 is an equidigital number, since it uses as much as digits as its factorization.

1668781669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5225472, while the sum is 58.

The square root of 1668781669 is about 40850.7242163465. The cubic root of 1668781669 is about 1186.1324120111.

The spelling of 1668781669 in words is "one billion, six hundred sixty-eight million, seven hundred eighty-one thousand, six hundred sixty-nine".