1685780779 has 2 divisors, whose sum is σ = 1685780780. Its totient is φ = 1685780778.

The previous prime is 1685780737. The next prime is 1685780797. The reversal of 1685780779 is 9770875861.

Together with next prime (1685780797) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1685780779 - 2²⁵ = 1652226347 is a prime.

It is not a weakly prime, because it can be changed into another prime (1685783779) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 842890389 + 842890390.

It is an arithmetic number, because the mean of its divisors is an integer number (842890390).

Almost surely, 2^1685780779 is an apocalyptic number.

1685780779 is a deficient number, since it is larger than the sum of its proper divisors (1).

1685780779 is an equidigital number, since it uses as much as digits as its factorization.

1685780779 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5927040, while the sum is 58.

The square root of 1685780779 is about 41058.2607887865. The cubic root of 1685780779 is about 1190.1463414877.

The spelling of 1685780779 in words is "one billion, six hundred eighty-five million, seven hundred eighty thousand, seven hundred seventy-nine".