28221921 has 48 divisors (see below), whose sum is σ = 53149824. Its totient is φ = 14003712.

The previous prime is 28221911. The next prime is 28221929. The reversal of 28221921 is 12912282.

It is not a de Polignac number, because 28221921 - 2⁷ = 28221793 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28221929) 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 47 ways as a sum of consecutive naturals, for example, 12910 + ... + 14936.

It is an arithmetic number, because the mean of its divisors is an integer number (1107288).

Almost surely, 2^28221921 is an apocalyptic number.

28221921 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28221921 is a deficient number, since it is larger than the sum of its proper divisors (24927903).

28221921 is a wasteful number, since it uses less digits than its factorization.

28221921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2070 (or 2067 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 28221921 is about 5312.4307995493. The cubic root of 28221921 is about 304.4590285172.

The spelling of 28221921 in words is "twenty-eight million, two hundred twenty-one thousand, nine hundred twenty-one".