8121278621 has 4 divisors (see below), whose sum is σ = 8124911292. Its totient is φ = 8117645952.

The previous prime is 8121278597. The next prime is 8121278651. The reversal of 8121278621 is 1268721218.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1268721218 = 2 ⋅634360609.

It can be written as a sum of positive squares in 2 ways, for example, as 6370274596 + 1751004025 = 79814^2 + 41845^2 .

It is a cyclic number.

It is not a de Polignac number, because 8121278621 - 2²² = 8117084317 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 (8121278651) 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, 1812980 + ... + 1817453.

It is an arithmetic number, because the mean of its divisors is an integer number (2031227823).

Almost surely, 2^8121278621 is an apocalyptic number.

It is an amenable number.

8121278621 is a deficient number, since it is larger than the sum of its proper divisors (3632671).

8121278621 is a wasteful number, since it uses less digits than its factorization.

8121278621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3632670.

The product of its digits is 21504, while the sum is 38.

The square root of 8121278621 is about 90118.1370257952. The cubic root of 8121278621 is about 2010.0559063846.

Adding to 8121278621 its reverse (1268721218), we get a palindrome (9389999839).

The spelling of 8121278621 in words is "eight billion, one hundred twenty-one million, two hundred seventy-eight thousand, six hundred twenty-one".