9819391861 has 2 divisors, whose sum is σ = 9819391862. Its totient is φ = 9819391860.

The previous prime is 9819391847. The next prime is 9819391871. The reversal of 9819391861 is 1681939189.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9275616100 + 543775761 = 96310^2 + 23319^2 .

It is a cyclic number.

It is not a de Polignac number, because 9819391861 - 2⁷ = 9819391733 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9819391831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4909695930 + 4909695931.

It is an arithmetic number, because the mean of its divisors is an integer number (4909695931).

Almost surely, 2^9819391861 is an apocalyptic number.

It is an amenable number.

9819391861 is a deficient number, since it is larger than the sum of its proper divisors (1).

9819391861 is an equidigital number, since it uses as much as digits as its factorization.

9819391861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 839808, while the sum is 55.

The square root of 9819391861 is about 99092.8446508627. The cubic root of 9819391861 is about 2141.3855310428.

The spelling of 9819391861 in words is "nine billion, eight hundred nineteen million, three hundred ninety-one thousand, eight hundred sixty-one".