8121809 has 4 divisors (see below), whose sum is σ = 8129520. Its totient is φ = 8114100.

The previous prime is 8121793. The next prime is 8121811. The reversal of 8121809 is 9081218.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9081218 = 2 ⋅4540609.

It is a cyclic number.

It is not a de Polignac number, because 8121809 - 2⁴ = 8121793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8121889) 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, 1967 + ... + 4484.

It is an arithmetic number, because the mean of its divisors is an integer number (2032380).

Almost surely, 2^8121809 is an apocalyptic number.

It is an amenable number.

8121809 is a deficient number, since it is larger than the sum of its proper divisors (7711).

8121809 is a wasteful number, since it uses less digits than its factorization.

8121809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7710.

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 8121809 is about 2849.8787693514. The cubic root of 8121809 is about 201.0099662558.

The spelling of 8121809 in words is "eight million, one hundred twenty-one thousand, eight hundred nine".