8121865720 has 16 divisors (see below), whose sum is σ = 18274197960. Its totient is φ = 3248746272.

The previous prime is 8121865673. The next prime is 8121865721. The reversal of 8121865720 is 275681218.

It is a super-2 number, since 2×8121865720² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (40), and also a Moran number because the ratio is a prime number: 203046643 = 8121865720 / (8 + 1 + 2 + 1 + 8 + 6 + 5 + 7 + 2 + 0).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8121865721) 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, 101523282 + ... + 101523361.

Almost surely, 2^8121865720 is an apocalyptic number.

It is an amenable number.

8121865720 is an abundant number, since it is smaller than the sum of its proper divisors (10152332240).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

8121865720 is a wasteful number, since it uses less digits than its factorization.

8121865720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203046654 (or 203046650 counting only the distinct ones).

The product of its (nonzero) digits is 53760, while the sum is 40.

The square root of 8121865720 is about 90121.3943522846. The cubic root of 8121865720 is about 2010.1043418355.

The spelling of 8121865720 in words is "eight billion, one hundred twenty-one million, eight hundred sixty-five thousand, seven hundred twenty".