999540991209581 has 2 divisors, whose sum is σ = 999540991209582. Its totient is φ = 999540991209580.

The previous prime is 999540991209529. The next prime is 999540991209587. The reversal of 999540991209581 is 185902199045999.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 995859711990025 + 3681279219556 = 31557245^2 + 1918666^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999540991209581 is a prime.

It is a super-2 number, since 2×999540991209581² (a number of 31 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 999540991209496 and 999540991209505.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999540991209587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499770495604790 + 499770495604791.

It is an arithmetic number, because the mean of its divisors is an integer number (499770495604791).

Almost surely, 2^{999540991209581} is an apocalyptic number.

It is an amenable number.

999540991209581 is a deficient number, since it is larger than the sum of its proper divisors (1).

999540991209581 is an equidigital number, since it uses as much as digits as its factorization.

999540991209581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 850305600, while the sum is 80.

The spelling of 999540991209581 in words is "nine hundred ninety-nine trillion, five hundred forty billion, nine hundred ninety-one million, two hundred nine thousand, five hundred eighty-one".