28243621 has 4 divisors (see below), whose sum is σ = 32278432. Its totient is φ = 24208812.

The previous prime is 28243603. The next prime is 28243643. The reversal of 28243621 is 12634282.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12634282 = 2 ⋅6317141.

It is a cyclic number.

It is not a de Polignac number, because 28243621 - 2⁹ = 28243109 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28243621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28243601) 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, 2017395 + ... + 2017408.

It is an arithmetic number, because the mean of its divisors is an integer number (8069608).

Almost surely, 2^28243621 is an apocalyptic number.

It is an amenable number.

28243621 is a deficient number, since it is larger than the sum of its proper divisors (4034811).

28243621 is an equidigital number, since it uses as much as digits as its factorization.

28243621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4034810.

The product of its digits is 4608, while the sum is 28.

The square root of 28243621 is about 5314.4727866459. The cubic root of 28243621 is about 304.5370419677.

The spelling of 28243621 in words is "twenty-eight million, two hundred forty-three thousand, six hundred twenty-one".