28138920 has 64 divisors (see below), whose sum is σ = 84870720. Its totient is φ = 7463424.

The previous prime is 28138897. The next prime is 28138937. The reversal of 28138920 is 2983182.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26724 + ... + 27756.

It is an arithmetic number, because the mean of its divisors is an integer number (1326105).

Almost surely, 2^28138920 is an apocalyptic number.

28138920 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 28138920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42435360).

28138920 is an abundant number, since it is smaller than the sum of its proper divisors (56731800).

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

28138920 is a wasteful number, since it uses less digits than its factorization.

28138920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1274 (or 1270 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 28138920 is about 5304.6130867387. The cubic root of 28138920 is about 304.1602629122.

The spelling of 28138920 in words is "twenty-eight million, one hundred thirty-eight thousand, nine hundred twenty".