28721418 has 48 divisors (see below), whose sum is σ = 64351584. Its totient is φ = 8475040.

The previous prime is 28721401. The next prime is 28721437. The reversal of 28721418 is 81412782.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 145696 + ... + 145892.

It is an arithmetic number, because the mean of its divisors is an integer number (1340658).

Almost surely, 2^28721418 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28721418, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32175792).

28721418 is an abundant number, since it is smaller than the sum of its proper divisors (35630166).

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

28721418 is a wasteful number, since it uses less digits than its factorization.

28721418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 307 (or 260 counting only the distinct ones).

The product of its digits is 7168, while the sum is 33.

The square root of 28721418 is about 5359.2366993817. The cubic root of 28721418 is about 306.2447313824.

The spelling of 28721418 in words is "twenty-eight million, seven hundred twenty-one thousand, four hundred eighteen".