28734721 has 4 divisors (see below), whose sum is σ = 29205844. Its totient is φ = 28263600.

The previous prime is 28734703. The next prime is 28734733. The reversal of 28734721 is 12743782.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5934096 + 22800625 = 2436^2 + 4775^2 .

It is a cyclic number.

It is not a de Polignac number, because 28734721 - 2¹¹ = 28732673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28734701) 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, 235470 + ... + 235591.

It is an arithmetic number, because the mean of its divisors is an integer number (7301461).

Almost surely, 2^28734721 is an apocalyptic number.

It is an amenable number.

28734721 is a deficient number, since it is larger than the sum of its proper divisors (471123).

28734721 is an equidigital number, since it uses as much as digits as its factorization.

28734721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 471122.

The product of its digits is 18816, while the sum is 34.

The square root of 28734721 is about 5360.4776839383. The cubic root of 28734721 is about 306.2920055668.

The spelling of 28734721 in words is "twenty-eight million, seven hundred thirty-four thousand, seven hundred twenty-one".