28021440 has 168 divisors, whose sum is σ = 95445072. Its totient is φ = 6963200.

The previous prime is 28021421. The next prime is 28021501. The reversal of 28021440 is 4412082.

28021440 = 156² + 157² + ... + 444².

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 277390 + ... + 277490.

Almost surely, 2^28021440 is an apocalyptic number.

28021440 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 28021440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47722536).

28021440 is an abundant number, since it is smaller than the sum of its proper divisors (67423632).

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

28021440 is a wasteful number, since it uses less digits than its factorization.

28021440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155 (or 128 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 28021440 is about 5293.5281240398. The cubic root of 28021440 is about 303.7363827322.

The spelling of 28021440 in words is "twenty-eight million, twenty-one thousand, four hundred forty".