28721807 has 4 divisors (see below), whose sum is σ = 29389800. Its totient is φ = 28053816.

The previous prime is 28721773. The next prime is 28721809. The reversal of 28721807 is 70812782.

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

It is a cyclic number.

It is not a de Polignac number, because 28721807 - 2⁶ = 28721743 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 (28721809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 333932 + ... + 334017.

It is an arithmetic number, because the mean of its divisors is an integer number (7347450).

Almost surely, 2^28721807 is an apocalyptic number.

28721807 is a deficient number, since it is larger than the sum of its proper divisors (667993).

28721807 is an equidigital number, since it uses as much as digits as its factorization.

28721807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 667992.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 28721807 is about 5359.2729917406. The cubic root of 28721807 is about 306.2461139587.

The spelling of 28721807 in words is "twenty-eight million, seven hundred twenty-one thousand, eight hundred seven".