28024721 has 4 divisors (see below), whose sum is σ = 29673252. Its totient is φ = 26376192.

The previous prime is 28024679. The next prime is 28024729. The reversal of 28024721 is 12742082.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12742082 = 2 ⋅6371041.

It can be written as a sum of positive squares in 2 ways, for example, as 18190225 + 9834496 = 4265^2 + 3136^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28024721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28024729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 824240 + ... + 824273.

It is an arithmetic number, because the mean of its divisors is an integer number (7418313).

Almost surely, 2^28024721 is an apocalyptic number.

It is an amenable number.

28024721 is a deficient number, since it is larger than the sum of its proper divisors (1648531).

28024721 is a wasteful number, since it uses less digits than its factorization.

28024721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1648530.

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 28024721 is about 5293.8380217003. The cubic root of 28024721 is about 303.7482369907.

The spelling of 28024721 in words is "twenty-eight million, twenty-four thousand, seven hundred twenty-one".