7220821 has 2 divisors, whose sum is σ = 7220822. Its totient is φ = 7220820.

The previous prime is 7220803. The next prime is 7220849. The reversal of 7220821 is 1280227.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4368100 + 2852721 = 2090^2 + 1689^2 .

It is a cyclic number.

It is not a de Polignac number, because 7220821 - 2⁵ = 7220789 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 7220792 and 7220801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7220891) 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, 3610410 + 3610411.

It is an arithmetic number, because the mean of its divisors is an integer number (3610411).

Almost surely, 2^7220821 is an apocalyptic number.

It is an amenable number.

7220821 is a deficient number, since it is larger than the sum of its proper divisors (1).

7220821 is an equidigital number, since it uses as much as digits as its factorization.

7220821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 7220821 is about 2687.1585364470. The cubic root of 7220821 is about 193.2838316256.

The spelling of 7220821 in words is "seven million, two hundred twenty thousand, eight hundred twenty-one".