1000991861 has 2 divisors, whose sum is σ = 1000991862. Its totient is φ = 1000991860.

The previous prime is 1000991833. The next prime is 1000991881. The reversal of 1000991861 is 1681990001.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 962922961 + 38068900 = 31031^2 + 6170^2 .

It is an emirp because it is prime and its reverse (1681990001) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1000991861 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1000991881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 500495930 + 500495931.

It is an arithmetic number, because the mean of its divisors is an integer number (500495931).

Almost surely, 2^1000991861 is an apocalyptic number.

It is an amenable number.

1000991861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1000991861 is an equidigital number, since it uses as much as digits as its factorization.

1000991861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 35.

The square root of 1000991861 is about 31638.4554142581. The cubic root of 1000991861 is about 1000.3305110837.

The spelling of 1000991861 in words is "one billion, nine hundred ninety-one thousand, eight hundred sixty-one".