221729 has 2 divisors, whose sum is σ = 221730. Its totient is φ = 221728.

The previous prime is 221723. The next prime is 221737. The reversal of 221729 is 927122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 200704 + 21025 = 448^2 + 145^2 .

It is a cyclic number.

It is not a de Polignac number, because 221729 - 2⁴ = 221713 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (221723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110864 + 110865.

It is an arithmetic number, because the mean of its divisors is an integer number (110865).

2²²¹⁷²⁹ is an apocalyptic number.

It is an amenable number.

221729 is a deficient number, since it is larger than the sum of its proper divisors (1).

221729 is an equidigital number, since it uses as much as digits as its factorization.

221729 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 504, while the sum is 23.

The square root of 221729 is about 470.8810890235. The cubic root of 221729 is about 60.5258410204.

The spelling of 221729 in words is "two hundred twenty-one thousand, seven hundred twenty-nine".