28724220 has 240 divisors, whose sum is σ = 109771200. Its totient is φ = 6137856.

The previous prime is 28724207. The next prime is 28724221. The reversal of 28724220 is 2242782.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Saint-Exupery number, since it is equal to the product of the sides of a Pythagorean triangle: 447 × 153 × 420.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28724221) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 192706 + ... + 192854.

It is an arithmetic number, because the mean of its divisors is an integer number (457380).

Almost surely, 2^28724220 is an apocalyptic number.

28724220 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 28724220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (54885600).

28724220 is an abundant number, since it is smaller than the sum of its proper divisors (81046980).

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

28724220 is a wasteful number, since it uses less digits than its factorization.

28724220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 194 (or 183 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 27.

The square root of 28724220 is about 5359.4981108309. The cubic root of 28724220 is about 306.2546899185.

The spelling of 28724220 in words is "twenty-eight million, seven hundred twenty-four thousand, two hundred twenty".