1678138909 has 2 divisors, whose sum is σ = 1678138910. Its totient is φ = 1678138908.

The previous prime is 1678138907. The next prime is 1678138921. The reversal of 1678138909 is 9098318761.

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., 1196468100 + 481670809 = 34590^2 + 21947^2 .

It is a cyclic number.

It is not a de Polignac number, because 1678138909 - 2¹ = 1678138907 is a prime.

Together with 1678138907, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1678138907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 839069454 + 839069455.

It is an arithmetic number, because the mean of its divisors is an integer number (839069455).

Almost surely, 2^1678138909 is an apocalyptic number.

It is an amenable number.

1678138909 is a deficient number, since it is larger than the sum of its proper divisors (1).

1678138909 is an equidigital number, since it uses as much as digits as its factorization.

1678138909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 653184, while the sum is 52.

The square root of 1678138909 is about 40965.0937872721. The cubic root of 1678138909 is about 1188.3452529720.

The spelling of 1678138909 in words is "one billion, six hundred seventy-eight million, one hundred thirty-eight thousand, nine hundred nine".