28530721 has 2 divisors, whose sum is σ = 28530722. Its totient is φ = 28530720.

The previous prime is 28530703. The next prime is 28530763. The reversal of 28530721 is 12703582.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20830096 + 7700625 = 4564^2 + 2775^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28530721 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28530721.

It is not a weakly prime, because it can be changed into another prime (28530701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14265360 + 14265361.

It is an arithmetic number, because the mean of its divisors is an integer number (14265361).

Almost surely, 2^28530721 is an apocalyptic number.

It is an amenable number.

28530721 is a deficient number, since it is larger than the sum of its proper divisors (1).

28530721 is an equidigital number, since it uses as much as digits as its factorization.

28530721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 28530721 is about 5341.4156363271. The cubic root of 28530721 is about 305.5654510857.

The spelling of 28530721 in words is "twenty-eight million, five hundred thirty thousand, seven hundred twenty-one".