28225721 has 2 divisors, whose sum is σ = 28225722. Its totient is φ = 28225720.

The previous prime is 28225667. The next prime is 28225723. The reversal of 28225721 is 12752282.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27678121 + 547600 = 5261^2 + 740^2 .

It is a cyclic number.

It is not a de Polignac number, because 28225721 - 2¹⁰ = 28224697 is a prime.

It is a Sophie Germain prime.

Together with 28225723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (28225723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14112860 + 14112861.

It is an arithmetic number, because the mean of its divisors is an integer number (14112861).

Almost surely, 2^28225721 is an apocalyptic number.

It is an amenable number.

28225721 is a deficient number, since it is larger than the sum of its proper divisors (1).

28225721 is an equidigital number, since it uses as much as digits as its factorization.

28225721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4480, while the sum is 29.

The square root of 28225721 is about 5312.7884392285. The cubic root of 28225721 is about 304.4726927463.

The spelling of 28225721 in words is "twenty-eight million, two hundred twenty-five thousand, seven hundred twenty-one".