8165903621 has 4 divisors (see below), whose sum is σ = 8365072044. Its totient is φ = 7966735200.

The previous prime is 8165903561. The next prime is 8165903639. The reversal of 8165903621 is 1263095618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1263095618 = 2 ⋅631547809.

It can be written as a sum of positive squares in 2 ways, for example, as 4273890625 + 3892012996 = 65375^2 + 62386^2 .

It is a cyclic number.

It is not a de Polignac number, because 8165903621 - 2¹⁰ = 8165902597 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41), and also a Moran number because the ratio is a prime number: 199168381 = 8165903621 / (8 + 1 + 6 + 5 + 9 + 0 + 3 + 6 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8165903021) 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, 99584150 + ... + 99584231.

It is an arithmetic number, because the mean of its divisors is an integer number (2091268011).

Almost surely, 2^8165903621 is an apocalyptic number.

It is an amenable number.

8165903621 is a deficient number, since it is larger than the sum of its proper divisors (199168423).

8165903621 is a wasteful number, since it uses less digits than its factorization.

8165903621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199168422.

The product of its (nonzero) digits is 77760, while the sum is 41.

The square root of 8165903621 is about 90365.3895083732. The cubic root of 8165903621 is about 2013.7308183352.

The spelling of 8165903621 in words is "eight billion, one hundred sixty-five million, nine hundred three thousand, six hundred twenty-one".