28393721 has 2 divisors, whose sum is σ = 28393722. Its totient is φ = 28393720.

The previous prime is 28393711. The next prime is 28393769. The reversal of 28393721 is 12739382.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 24393721 + 4000000 = 4939^2 + 2000^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28393721 is a prime.

It is not a weakly prime, because it can be changed into another prime (28393711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14196860 + 14196861.

It is an arithmetic number, because the mean of its divisors is an integer number (14196861).

Almost surely, 2^28393721 is an apocalyptic number.

It is an amenable number.

28393721 is a deficient number, since it is larger than the sum of its proper divisors (1).

28393721 is an equidigital number, since it uses as much as digits as its factorization.

28393721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 35.

The square root of 28393721 is about 5328.5758885466. The cubic root of 28393721 is about 305.0755738552.

The spelling of 28393721 in words is "twenty-eight million, three hundred ninety-three thousand, seven hundred twenty-one".