28221500 has 24 divisors (see below), whose sum is σ = 61636848. Its totient is φ = 11288400.

The previous prime is 28221499. The next prime is 28221509. The reversal of 28221500 is 512282.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28221509) 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, 27722 + ... + 28721.

It is an arithmetic number, because the mean of its divisors is an integer number (2568202).

Almost surely, 2^28221500 is an apocalyptic number.

28221500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28221500 is an abundant number, since it is smaller than the sum of its proper divisors (33415348).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28221500 is a wasteful number, since it uses less digits than its factorization.

28221500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56462 (or 56450 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 28221500 is about 5312.3911753560. The cubic root of 28221500 is about 304.4575145890.

Adding to 28221500 its reverse (512282), we get a palindrome (28733782).

The spelling of 28221500 in words is "twenty-eight million, two hundred twenty-one thousand, five hundred".