28721783 has 4 divisors (see below), whose sum is σ = 28814448. Its totient is φ = 28629120.

The previous prime is 28721773. The next prime is 28721809. The reversal of 28721783 is 38712782.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 38712782 = 2 ⋅19356391.

It is a cyclic number.

It is not a de Polignac number, because 28721783 - 2⁴ = 28721767 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 (28721713) 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, 45866 + ... + 46487.

It is an arithmetic number, because the mean of its divisors is an integer number (7203612).

Almost surely, 2^28721783 is an apocalyptic number.

28721783 is a deficient number, since it is larger than the sum of its proper divisors (92665).

28721783 is an equidigital number, since it uses as much as digits as its factorization.

28721783 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92664.

The product of its digits is 37632, while the sum is 38.

The square root of 28721783 is about 5359.2707526304. The cubic root of 28721783 is about 306.2460286588.

Subtracting 28721783 from its reverse (38712782), we obtain a palindrome (9990999).

The spelling of 28721783 in words is "twenty-eight million, seven hundred twenty-one thousand, seven hundred eighty-three".