1981863109 has 2 divisors, whose sum is σ = 1981863110. Its totient is φ = 1981863108.

The previous prime is 1981863097. The next prime is 1981863131. The reversal of 1981863109 is 9013681891.

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., 1080962884 + 900900225 = 32878^2 + 30015^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981863109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981863199) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990931554 + 990931555.

It is an arithmetic number, because the mean of its divisors is an integer number (990931555).

Almost surely, 2^1981863109 is an apocalyptic number.

It is an amenable number.

1981863109 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981863109 is an equidigital number, since it uses as much as digits as its factorization.

1981863109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 93312, while the sum is 46.

The square root of 1981863109 is about 44518.1211306138. The cubic root of 1981863109 is about 1256.1009706665.

It can be divided in two parts, 198186 and 3109, that added together give a triangular number (201295 = T₆₃₄).

The spelling of 1981863109 in words is "one billion, nine hundred eighty-one million, eight hundred sixty-three thousand, one hundred nine".