28438221 has 16 divisors (see below), whose sum is σ = 43679744. Its totient is φ = 16120944.

The previous prime is 28438213. The next prime is 28438247. The reversal of 28438221 is 12283482.

It is not a de Polignac number, because 28438221 - 2³ = 28438213 is a prime.

It is a super-3 number, since 3×28438221³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28438211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2665 + ... + 7998.

It is an arithmetic number, because the mean of its divisors is an integer number (2729984).

Almost surely, 2^28438221 is an apocalyptic number.

28438221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28438221 is a deficient number, since it is larger than the sum of its proper divisors (15241523).

28438221 is a wasteful number, since it uses less digits than its factorization.

28438221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10800.

The product of its digits is 6144, while the sum is 30.

The square root of 28438221 is about 5332.7498534996. The cubic root of 28438221 is about 305.2348670191.

The spelling of 28438221 in words is "twenty-eight million, four hundred thirty-eight thousand, two hundred twenty-one".