8187821 has 4 divisors (see below), whose sum is σ = 8206044. Its totient is φ = 8169600.

The previous prime is 8187799. The next prime is 8187827. The reversal of 8187821 is 1287818.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2758921 + 5428900 = 1661^2 + 2330^2 .

It is a cyclic number.

It is not a de Polignac number, because 8187821 - 2⁶ = 8187757 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8187827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8420 + ... + 9341.

It is an arithmetic number, because the mean of its divisors is an integer number (2051511).

Almost surely, 2^8187821 is an apocalyptic number.

It is an amenable number.

8187821 is a deficient number, since it is larger than the sum of its proper divisors (18223).

8187821 is a wasteful number, since it uses less digits than its factorization.

8187821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18222.

The product of its digits is 7168, while the sum is 35.

The square root of 8187821 is about 2861.4368768156. The cubic root of 8187821 is about 201.5530834413.

The spelling of 8187821 in words is "eight million, one hundred eighty-seven thousand, eight hundred twenty-one".