28387621 has 8 divisors (see below), whose sum is σ = 29867544. Its totient is φ = 26945280.

The previous prime is 28387573. The next prime is 28387627. The reversal of 28387621 is 12678382.

It can be written as a sum of positive squares in 4 ways, for example, as 6400900 + 21986721 = 2530^2 + 4689^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 28387621 - 2¹¹ = 28385573 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28387627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7840 + ... + 10873.

It is an arithmetic number, because the mean of its divisors is an integer number (3733443).

Almost surely, 2^28387621 is an apocalyptic number.

It is an amenable number.

28387621 is a deficient number, since it is larger than the sum of its proper divisors (1479923).

28387621 is a wasteful number, since it uses less digits than its factorization.

28387621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18791.

The product of its digits is 32256, while the sum is 37.

The square root of 28387621 is about 5328.0034722211. The cubic root of 28387621 is about 305.0537251950.

Subtracting from 28387621 its sum of digits (37), we obtain a square (28387584 = 5328²).

The spelling of 28387621 in words is "twenty-eight million, three hundred eighty-seven thousand, six hundred twenty-one".