8720621617 has 2 divisors, whose sum is σ = 8720621618. Its totient is φ = 8720621616.

The previous prime is 8720621551. The next prime is 8720621621. The reversal of 8720621617 is 7161260278.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5697381361 + 3023240256 = 75481^2 + 54984^2 .

It is a cyclic number.

It is not a de Polignac number, because 8720621617 - 2¹¹ = 8720619569 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 8720621617.

It is not a weakly prime, because it can be changed into another prime (8720661617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4360310808 + 4360310809.

It is an arithmetic number, because the mean of its divisors is an integer number (4360310809).

Almost surely, 2^8720621617 is an apocalyptic number.

It is an amenable number.

8720621617 is a deficient number, since it is larger than the sum of its proper divisors (1).

8720621617 is an equidigital number, since it uses as much as digits as its factorization.

8720621617 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 56448, while the sum is 40.

The square root of 8720621617 is about 93384.2685734594. The cubic root of 8720621617 is about 2058.3338411898. Note that the first 3 decimals are identical.

The spelling of 8720621617 in words is "eight billion, seven hundred twenty million, six hundred twenty-one thousand, six hundred seventeen".