220721 has 2 divisors, whose sum is σ = 220722. Its totient is φ = 220720.

The previous prime is 220709. The next prime is 220747. The reversal of 220721 is 127022.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 190096 + 30625 = 436^2 + 175^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-220721 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 220696 and 220705.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 220721.

It is not a weakly prime, because it can be changed into another prime (220771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110360 + 110361.

It is an arithmetic number, because the mean of its divisors is an integer number (110361).

2²²⁰⁷²¹ is an apocalyptic number.

It is an amenable number.

220721 is a deficient number, since it is larger than the sum of its proper divisors (1).

220721 is an equidigital number, since it uses as much as digits as its factorization.

220721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 56, while the sum is 14.

The square root of 220721 is about 469.8095358760. The cubic root of 220721 is about 60.4339830401.

Adding to 220721 its reverse (127022), we get a palindrome (347743).

The spelling of 220721 in words is "two hundred twenty thousand, seven hundred twenty-one", and thus it is an iban number.