8720621621 has 2 divisors, whose sum is σ = 8720621622. Its totient is φ = 8720621620.

The previous prime is 8720621617. The next prime is 8720621629. The reversal of 8720621621 is 1261260278.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6080100625 + 2640520996 = 77975^2 + 51386^2 .

It is a cyclic number.

It is not a de Polignac number, because 8720621621 - 2² = 8720621617 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8720621629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4360310810 + 4360310811.

It is an arithmetic number, because the mean of its divisors is an integer number (4360310811).

Almost surely, 2^8720621621 is an apocalyptic number.

It is an amenable number.

8720621621 is a deficient number, since it is larger than the sum of its proper divisors (1).

8720621621 is an equidigital number, since it uses as much as digits as its factorization.

8720621621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 8720621621 is about 93384.2685948763. The cubic root of 8720621621 is about 2058.3338415045. Note that the first 3 decimals are identical.

Adding to 8720621621 its reverse (1261260278), we get a palindrome (9981881899).

The spelling of 8720621621 in words is "eight billion, seven hundred twenty million, six hundred twenty-one thousand, six hundred twenty-one".