28644721 has 8 divisors (see below), whose sum is σ = 33865920. Its totient is φ = 23705808.

The previous prime is 28644719. The next prime is 28644731. The reversal of 28644721 is 12744682.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 28644721 - 2¹ = 28644719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28644701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 70351 + ... + 70756.

It is an arithmetic number, because the mean of its divisors is an integer number (4233240).

Almost surely, 2^28644721 is an apocalyptic number.

It is an amenable number.

28644721 is a deficient number, since it is larger than the sum of its proper divisors (5221199).

28644721 is a wasteful number, since it uses less digits than its factorization.

28644721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141143.

The product of its digits is 21504, while the sum is 34.

The square root of 28644721 is about 5352.0763260626. The cubic root of 28644721 is about 305.9718921311.

The spelling of 28644721 in words is "twenty-eight million, six hundred forty-four thousand, seven hundred twenty-one".