1981719521 has 2 divisors, whose sum is σ = 1981719522. Its totient is φ = 1981719520.

The previous prime is 1981719499. The next prime is 1981719527. The reversal of 1981719521 is 1259171891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1725239296 + 256480225 = 41536^2 + 16015^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981719521 - 2²⁶ = 1914610657 is a prime.

It is not a weakly prime, because it can be changed into another prime (1981719527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990859760 + 990859761.

It is an arithmetic number, because the mean of its divisors is an integer number (990859761).

Almost surely, 2^1981719521 is an apocalyptic number.

It is an amenable number.

1981719521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981719521 is an equidigital number, since it uses as much as digits as its factorization.

1981719521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45360, while the sum is 44.

The square root of 1981719521 is about 44516.5084098023. The cubic root of 1981719521 is about 1256.0706346691.

The spelling of 1981719521 in words is "one billion, nine hundred eighty-one million, seven hundred nineteen thousand, five hundred twenty-one".