28297440 has 144 divisors (see below), whose sum is σ = 99026928. Its totient is φ = 7354368.

The previous prime is 28297433. The next prime is 28297463. The reversal of 28297440 is 4479282.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×28297440² = 1601490221107200, which contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 28297395 and 28297404.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 61692 + ... + 62148.

It is an arithmetic number, because the mean of its divisors is an integer number (687687).

Almost surely, 2^28297440 is an apocalyptic number.

28297440 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 28297440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49513464).

28297440 is an abundant number, since it is smaller than the sum of its proper divisors (70729488).

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

28297440 is a wasteful number, since it uses less digits than its factorization.

28297440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521 (or 510 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The square root of 28297440 is about 5319.5338141608. The cubic root of 28297440 is about 304.7303538146.

The spelling of 28297440 in words is "twenty-eight million, two hundred ninety-seven thousand, four hundred forty".