280138721 has 4 divisors (see below), whose sum is σ = 280605444. Its totient is φ = 279672000.

The previous prime is 280138709. The next prime is 280138757. The reversal of 280138721 is 127831082.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 256480225 + 23658496 = 16015^2 + 4864^2 .

It is a cyclic number.

It is not a de Polignac number, because 280138721 - 2¹⁸ = 279876577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (280158721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 232460 + ... + 233661.

It is an arithmetic number, because the mean of its divisors is an integer number (70151361).

Almost surely, 2^280138721 is an apocalyptic number.

It is an amenable number.

280138721 is a deficient number, since it is larger than the sum of its proper divisors (466723).

280138721 is an equidigital number, since it uses as much as digits as its factorization.

280138721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 466722.

The product of its (nonzero) digits is 5376, while the sum is 32.

The square root of 280138721 is about 16737.3451001047. The cubic root of 280138721 is about 654.3212836267.

The spelling of 280138721 in words is "two hundred eighty million, one hundred thirty-eight thousand, seven hundred twenty-one".