100820991 has 4 divisors (see below), whose sum is σ = 134427992. Its totient is φ = 67213992.

The previous prime is 100820989. The next prime is 100821001. The reversal of 100820991 is 199028001.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 100820991 - 2¹ = 100820989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (100820981) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16803496 + ... + 16803501.

It is an arithmetic number, because the mean of its divisors is an integer number (33606998).

Almost surely, 2^100820991 is an apocalyptic number.

100820991 is a deficient number, since it is larger than the sum of its proper divisors (33607001).

100820991 is an equidigital number, since it uses as much as digits as its factorization.

100820991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33607000.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 100820991 is about 10040.9656408136. The cubic root of 100820991 is about 465.4256571799.

Adding to 100820991 its reverse (199028001), we get a palindrome (299848992).

The spelling of 100820991 in words is "one hundred million, eight hundred twenty thousand, nine hundred ninety-one".