28221507 has 8 divisors (see below), whose sum is σ = 41809680. Its totient is φ = 18814320.

The previous prime is 28221499. The next prime is 28221509. The reversal of 28221507 is 70512282.

It is not a de Polignac number, because 28221507 - 2³ = 28221499 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 1045241 = 28221507 / (2 + 8 + 2 + 2 + 1 + 5 + 0 + 7).

It is not an unprimeable number, because it can be changed into a prime (28221509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 522594 + ... + 522647.

It is an arithmetic number, because the mean of its divisors is an integer number (5226210).

Almost surely, 2^28221507 is an apocalyptic number.

28221507 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

28221507 is a deficient number, since it is larger than the sum of its proper divisors (13588173).

28221507 is a wasteful number, since it uses less digits than its factorization.

28221507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1045250 (or 1045244 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 28221507 is about 5312.3918341930. The cubic root of 28221507 is about 304.4575397613.

Adding to 28221507 its reverse (70512282), we get a palindrome (98733789).

The spelling of 28221507 in words is "twenty-eight million, two hundred twenty-one thousand, five hundred seven".