100005991 has 2 divisors, whose sum is σ = 100005992. Its totient is φ = 100005990.

The previous prime is 100005973. The next prime is 100006033. The reversal of 100005991 is 199500001.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-100005991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (100005091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50002995 + 50002996.

It is an arithmetic number, because the mean of its divisors is an integer number (50002996).

Almost surely, 2^100005991 is an apocalyptic number.

100005991 is a deficient number, since it is larger than the sum of its proper divisors (1).

100005991 is an equidigital number, since it uses as much as digits as its factorization.

100005991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 405, while the sum is 25.

The square root of 100005991 is about 10000.2995455136. The cubic root of 100005991 is about 464.1681524291.

Adding to 100005991 its reverse (199500001), we get a palindrome (299505992).

The spelling of 100005991 in words is "one hundred million, five thousand, nine hundred ninety-one".