28947221 has 8 divisors (see below), whose sum is σ = 29240640. Its totient is φ = 28655712.

The previous prime is 28947181. The next prime is 28947251. The reversal of 28947221 is 12274982.

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

It is a cyclic number.

It is not a de Polignac number, because 28947221 - 2⁶ = 28947157 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28947251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65720 + ... + 66158.

It is an arithmetic number, because the mean of its divisors is an integer number (3655080).

Almost surely, 2^28947221 is an apocalyptic number.

It is an amenable number.

28947221 is a deficient number, since it is larger than the sum of its proper divisors (293419).

28947221 is a wasteful number, since it uses less digits than its factorization.

28947221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 955.

The product of its digits is 16128, while the sum is 35.

The square root of 28947221 is about 5380.2621683334. The cubic root of 28947221 is about 307.0451856941.

The spelling of 28947221 in words is "twenty-eight million, nine hundred forty-seven thousand, two hundred twenty-one".