281228721 has 4 divisors (see below), whose sum is σ = 374971632. Its totient is φ = 187485812.

The previous prime is 281228719. The next prime is 281228767. The reversal of 281228721 is 127822182.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 281228721 - 2¹ = 281228719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (281228021) 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, 46871451 + ... + 46871456.

It is an arithmetic number, because the mean of its divisors is an integer number (93742908).

Almost surely, 2^281228721 is an apocalyptic number.

It is an amenable number.

281228721 is a deficient number, since it is larger than the sum of its proper divisors (93742911).

281228721 is an equidigital number, since it uses as much as digits as its factorization.

281228721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93742910.

The product of its digits is 7168, while the sum is 33.

The square root of 281228721 is about 16769.8754020416. The cubic root of 281228721 is about 655.1688246522.

The spelling of 281228721 in words is "two hundred eighty-one million, two hundred twenty-eight thousand, seven hundred twenty-one".