281621 has 2 divisors, whose sum is σ = 281622. Its totient is φ = 281620.

The previous prime is 281609. The next prime is 281623. The reversal of 281621 is 126182.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 184900 + 96721 = 430^2 + 311^2 .

It is a cyclic number.

It is not a de Polignac number, because 281621 - 2⁶ = 281557 is a prime.

Together with 281623, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 281593 and 281602.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 281621.

It is not a weakly prime, because it can be changed into another prime (281623) 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, 140810 + 140811.

It is an arithmetic number, because the mean of its divisors is an integer number (140811).

2²⁸¹⁶²¹ is an apocalyptic number.

It is an amenable number.

281621 is a deficient number, since it is larger than the sum of its proper divisors (1).

281621 is an equidigital number, since it uses as much as digits as its factorization.

281621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 192, while the sum is 20.

The square root of 281621 is about 530.6797527700. The cubic root of 281621 is about 65.5473309396.

The spelling of 281621 in words is "two hundred eighty-one thousand, six hundred twenty-one".