8621721 has 10 divisors (see below), whose sum is σ = 12879482. Its totient is φ = 5747760.

The previous prime is 8621707. The next prime is 8621747. The reversal of 8621721 is 1271268.

It can be written as a sum of positive squares in only one way, i.e., 4665600 + 3956121 = 2160^2 + 1989^2 .

It is not a de Polignac number, because 8621721 - 2⁹ = 8621209 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (8620721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 53140 + ... + 53301.

Almost surely, 2^8621721 is an apocalyptic number.

8621721 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

8621721 is a deficient number, since it is larger than the sum of its proper divisors (4257761).

8621721 is a wasteful number, since it uses less digits than its factorization.

8621721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106453 (or 106444 counting only the distinct ones).

The product of its digits is 1344, while the sum is 27.

The square root of 8621721 is about 2936.2767240163. The cubic root of 8621721 is about 205.0523047182.

Adding to 8621721 its reverse (1271268), we get a palindrome (9892989).

The spelling of 8621721 in words is "eight million, six hundred twenty-one thousand, seven hundred twenty-one".