28209720 has 256 divisors, whose sum is σ = 109486080. Its totient is φ = 5644800.

The previous prime is 28209719. The next prime is 28209739. The reversal of 28209720 is 2790282.

28209720 = 595² + 596² + ... + 665².

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

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 63 ways as a sum of consecutive naturals, for example, 397285 + ... + 397355.

It is an arithmetic number, because the mean of its divisors is an integer number (427680).

Almost surely, 2^28209720 is an apocalyptic number.

28209720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28209720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (54743040).

28209720 is an abundant number, since it is smaller than the sum of its proper divisors (81276360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28209720 is a wasteful number, since it uses less digits than its factorization.

28209720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 28209720 is about 5311.2823310383. The cubic root of 28209720 is about 304.4151472608.

The spelling of 28209720 in words is "twenty-eight million, two hundred nine thousand, seven hundred twenty".