281721 has 8 divisors (see below), whose sum is σ = 409824. Its totient is φ = 170720.

The previous prime is 281719. The next prime is 281737. The reversal of 281721 is 127182.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 281721 - 2¹ = 281719 is a prime.

281721 is a lucky number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 281721.

It is not an unprimeable number, because it can be changed into a prime (281761) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4236 + ... + 4301.

It is an arithmetic number, because the mean of its divisors is an integer number (51228).

2²⁸¹⁷²¹ is an apocalyptic number.

It is an amenable number.

281721 is a deficient number, since it is larger than the sum of its proper divisors (128103).

281721 is a wasteful number, since it uses less digits than its factorization.

281721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8551.

The product of its digits is 224, while the sum is 21.

The square root of 281721 is about 530.7739631896. The cubic root of 281721 is about 65.5550883600. Note that the first 3 decimals are identical.

The spelling of 281721 in words is "two hundred eighty-one thousand, seven hundred twenty-one".