19805861 has 2 divisors, whose sum is σ = 19805862. Its totient is φ = 19805860.

The previous prime is 19805857. The next prime is 19805879. The reversal of 19805861 is 16850891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16760836 + 3045025 = 4094^2 + 1745^2 .

It is a cyclic number.

It is not a de Polignac number, because 19805861 - 2² = 19805857 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19805801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9902930 + 9902931.

It is an arithmetic number, because the mean of its divisors is an integer number (9902931).

Almost surely, 2^19805861 is an apocalyptic number.

It is an amenable number.

19805861 is a deficient number, since it is larger than the sum of its proper divisors (1).

19805861 is an equidigital number, since it uses as much as digits as its factorization.

19805861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 38.

The square root of 19805861 is about 4450.3776244269. The cubic root of 19805861 is about 270.5606138574.

The spelling of 19805861 in words is "nineteen million, eight hundred five thousand, eight hundred sixty-one".