100821605 has 4 divisors (see below), whose sum is σ = 120985932. Its totient is φ = 80657280.

The previous prime is 100821587. The next prime is 100821613. The reversal of 100821605 is 506128001.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 506128001 = 271 ⋅1867631.

It can be written as a sum of positive squares in 2 ways, for example, as 65383396 + 35438209 = 8086^2 + 5953^2 .

It is not a de Polignac number, because 100821605 - 2¹⁰ = 100820581 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 10082156 + ... + 10082165.

It is an arithmetic number, because the mean of its divisors is an integer number (30246483).

Almost surely, 2^100821605 is an apocalyptic number.

It is an amenable number.

100821605 is a deficient number, since it is larger than the sum of its proper divisors (20164327).

100821605 is an equidigital number, since it uses as much as digits as its factorization.

100821605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20164326.

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 100821605 is about 10040.9962155157. The cubic root of 100821605 is about 465.4266019923.

Adding to 100821605 its reverse (506128001), we get a palindrome (606949606).

The spelling of 100821605 in words is "one hundred million, eight hundred twenty-one thousand, six hundred five".