100820581 has 2 divisors, whose sum is σ = 100820582. Its totient is φ = 100820580.

The previous prime is 100820579. The next prime is 100820609. The reversal of 100820581 is 185028001.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67076100 + 33744481 = 8190^2 + 5809^2 .

It is a cyclic number.

It is not a de Polignac number, because 100820581 - 2¹ = 100820579 is a prime.

It is a super-2 number, since 2×100820581² = 20329579106355122, which contains 22 as substring.

Together with 100820579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (100820561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50410290 + 50410291.

It is an arithmetic number, because the mean of its divisors is an integer number (50410291).

Almost surely, 2^100820581 is an apocalyptic number.

It is an amenable number.

100820581 is a deficient number, since it is larger than the sum of its proper divisors (1).

100820581 is an equidigital number, since it uses as much as digits as its factorization.

100820581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 640, while the sum is 25.

The square root of 100820581 is about 10040.9452244298. The cubic root of 100820581 is about 465.4250262769.

Adding to 100820581 its reverse (185028001), we get a palindrome (285848582).

The spelling of 100820581 in words is "one hundred million, eight hundred twenty thousand, five hundred eighty-one".