1999999861 has 2 divisors, whose sum is σ = 1999999862. Its totient is φ = 1999999860.

The previous prime is 1999999853. The next prime is 1999999871. The reversal of 1999999861 is 1689999991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1637820900 + 362178961 = 40470^2 + 19031^2 .

It is a cyclic number.

It is not a de Polignac number, because 1999999861 - 2³ = 1999999853 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1999999811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999999930 + 999999931.

It is an arithmetic number, because the mean of its divisors is an integer number (999999931).

Almost surely, 2^1999999861 is an apocalyptic number.

It is an amenable number.

1999999861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1999999861 is an equidigital number, since it uses as much as digits as its factorization.

1999999861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25509168, while the sum is 70.

The square root of 1999999861 is about 44721.3579959285. The cubic root of 1999999861 is about 1259.9210207067.

The spelling of 1999999861 in words is "one billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, eight hundred sixty-one".