28909440 has 256 divisors, whose sum is σ = 117504000. Its totient is φ = 6580224.

The previous prime is 28909409. The next prime is 28909451. The reversal of 28909440 is 4490982.

It is a happy number.

It is a super-2 number, since 2×28909440² = 1671511442227200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 28909395 and 28909404.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 120841 + ... + 121079.

It is an arithmetic number, because the mean of its divisors is an integer number (459000).

Almost surely, 2^28909440 is an apocalyptic number.

28909440 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 28909440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (58752000).

28909440 is an abundant number, since it is smaller than the sum of its proper divisors (88594560).

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

28909440 is a wasteful number, since it uses less digits than its factorization.

28909440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 274 (or 256 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 28909440 is about 5376.7499476914. The cubic root of 28909440 is about 306.9115456384.

The spelling of 28909440 in words is "twenty-eight million, nine hundred nine thousand, four hundred forty".