28912821 has 16 divisors (see below), whose sum is σ = 44488704. Its totient is φ = 16359984.

The previous prime is 28912811. The next prime is 28912843. The reversal of 28912821 is 12821982.

It is not a de Polignac number, because 28912821 - 2⁵ = 28912789 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28912811) 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, 4521 + ... + 8846.

It is an arithmetic number, because the mean of its divisors is an integer number (2780544).

Almost surely, 2^28912821 is an apocalyptic number.

28912821 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28912821 is a deficient number, since it is larger than the sum of its proper divisors (15575883).

28912821 is a wasteful number, since it uses less digits than its factorization.

28912821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13480.

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

The square root of 28912821 is about 5377.0643477645. The cubic root of 28912821 is about 306.9235097522.

The spelling of 28912821 in words is "twenty-eight million, nine hundred twelve thousand, eight hundred twenty-one".