28623821 has 4 divisors (see below), whose sum is σ = 28832892. Its totient is φ = 28414752.

The previous prime is 28623809. The next prime is 28623839. The reversal of 28623821 is 12832682.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9796900 + 18826921 = 3130^2 + 4339^2 .

It is a cyclic number.

It is not a de Polignac number, because 28623821 - 2¹⁴ = 28607437 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28623851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104330 + ... + 104603.

It is an arithmetic number, because the mean of its divisors is an integer number (7208223).

Almost surely, 2^28623821 is an apocalyptic number.

It is an amenable number.

28623821 is a deficient number, since it is larger than the sum of its proper divisors (209071).

28623821 is a wasteful number, since it uses less digits than its factorization.

28623821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209070.

The product of its digits is 9216, while the sum is 32.

The square root of 28623821 is about 5350.1234565195. The cubic root of 28623821 is about 305.8974587715.

The spelling of 28623821 in words is "twenty-eight million, six hundred twenty-three thousand, eight hundred twenty-one".