280921 has 2 divisors, whose sum is σ = 280922. Its totient is φ = 280920.

The previous prime is 280913. The next prime is 280927. The reversal of 280921 is 129082.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151321 + 129600 = 389^2 + 360^2 .

It is a cyclic number.

It is not a de Polignac number, because 280921 - 2³ = 280913 is a prime.

280921 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 280892 and 280901.

It is not a weakly prime, because it can be changed into another prime (280927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 140460 + 140461.

It is an arithmetic number, because the mean of its divisors is an integer number (140461).

2²⁸⁰⁹²¹ is an apocalyptic number.

It is an amenable number.

280921 is a deficient number, since it is larger than the sum of its proper divisors (1).

280921 is an equidigital number, since it uses as much as digits as its factorization.

280921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 280921 is about 530.0198109505. The cubic root of 280921 is about 65.4929775118.

The spelling of 280921 in words is "two hundred eighty thousand, nine hundred twenty-one".