28028621 has 4 divisors (see below), whose sum is σ = 28046172. Its totient is φ = 28011072.

The previous prime is 28028593. The next prime is 28028641. The reversal of 28028621 is 12682082.

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 15319396 + 12709225 = 3914^2 + 3565^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28028621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28028641) 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, 6110 + ... + 9663.

It is an arithmetic number, because the mean of its divisors is an integer number (7011543).

Almost surely, 2^28028621 is an apocalyptic number.

It is an amenable number.

28028621 is a deficient number, since it is larger than the sum of its proper divisors (17551).

28028621 is a wasteful number, since it uses less digits than its factorization.

28028621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17550.

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 28028621 is about 5294.2063616750. The cubic root of 28028621 is about 303.7623264937.

The spelling of 28028621 in words is "twenty-eight million, twenty-eight thousand, six hundred twenty-one".