285721 has 2 divisors, whose sum is σ = 285722. Its totient is φ = 285720.

The previous prime is 285709. The next prime is 285731. The reversal of 285721 is 127582.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 250000 + 35721 = 500^2 + 189^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-285721 is a prime.

It is a d-powerful number, because it can be written as 2¹¹ + 8⁴ + 7⁵ + 5⁴ + 2¹⁸ + 1 .

It is not a weakly prime, because it can be changed into another prime (285731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 142860 + 142861.

It is an arithmetic number, because the mean of its divisors is an integer number (142861).

285721 is a Friedman number, since it can be written as 2+7^5*(8*2+1), using all its digits and the basic arithmetic operations.

2²⁸⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

285721 is a deficient number, since it is larger than the sum of its proper divisors (1).

285721 is an equidigital number, since it uses as much as digits as its factorization.

285721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1120, while the sum is 25.

The square root of 285721 is about 534.5287644271. The cubic root of 285721 is about 65.8638915266.

The spelling of 285721 in words is "two hundred eighty-five thousand, seven hundred twenty-one".