287721 has 12 divisors (see below), whose sum is σ = 475072. Its totient is φ = 164376.

The previous prime is 287701. The next prime is 287731. The reversal of 287721 is 127782.

It is not a de Polignac number, because 287721 - 2⁵ = 287689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (287701) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2221 + ... + 2346.

2²⁸⁷⁷²¹ is an apocalyptic number.

287721 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

287721 is a deficient number, since it is larger than the sum of its proper divisors (187351).

287721 is a wasteful number, since it uses less digits than its factorization.

287721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4580 (or 4577 counting only the distinct ones).

The product of its digits is 1568, while the sum is 27.

The square root of 287721 is about 536.3963087121. The cubic root of 287721 is about 66.0172131412.

The spelling of 287721 in words is "two hundred eighty-seven thousand, seven hundred twenty-one".