28921821 has 8 divisors (see below), whose sum is σ = 39050880. Its totient is φ = 19036992.

The previous prime is 28921817. The next prime is 28921829. The reversal of 28921821 is 12812982.

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

It is not a de Polignac number, because 28921821 - 2² = 28921817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28921829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 60780 + ... + 61253.

It is an arithmetic number, because the mean of its divisors is an integer number (4881360).

Almost surely, 2^28921821 is an apocalyptic number.

It is an amenable number.

28921821 is a deficient number, since it is larger than the sum of its proper divisors (10129059).

28921821 is a wasteful number, since it uses less digits than its factorization.

28921821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 122115.

The product of its digits is 4608, while the sum is 33.

The square root of 28921821 is about 5377.9011705311. The cubic root of 28921821 is about 306.9553528922.

The spelling of 28921821 in words is "twenty-eight million, nine hundred twenty-one thousand, eight hundred twenty-one".