28787720 has 128 divisors (see below), whose sum is σ = 76204800. Its totient is φ = 9698304.

The previous prime is 28787713. The next prime is 28787729. The reversal of 28787720 is 2778782.

28787720 = 66² + 67² + ... + 442².

It is not an unprimeable number, because it can be changed into a prime (28787729) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 346799 + ... + 346881.

It is an arithmetic number, because the mean of its divisors is an integer number (595350).

Almost surely, 2^28787720 is an apocalyptic number.

28787720 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 28787720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38102400).

28787720 is an abundant number, since it is smaller than the sum of its proper divisors (47417080).

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

28787720 is a wasteful number, since it uses less digits than its factorization.

28787720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159 (or 155 counting only the distinct ones).

The product of its (nonzero) digits is 87808, while the sum is 41.

The square root of 28787720 is about 5365.4189025648. The cubic root of 28787720 is about 306.4802006536.

The spelling of 28787720 in words is "twenty-eight million, seven hundred eighty-seven thousand, seven hundred twenty".