28221520 has 40 divisors (see below), whose sum is σ = 66011400. Its totient is φ = 11220480.

The previous prime is 28221511. The next prime is 28221533. The reversal of 28221520 is 2512282.

It can be written as a sum of positive squares in 4 ways, for example, as 595984 + 27625536 = 772^2 + 5256^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×28221520² = 1592908382220800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 28221491 and 28221500.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13506 + ... + 15454.

It is an arithmetic number, because the mean of its divisors is an integer number (1650285).

Almost surely, 2^28221520 is an apocalyptic number.

28221520 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 28221520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33005700).

28221520 is an abundant number, since it is smaller than the sum of its proper divisors (37789880).

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

28221520 is a wasteful number, since it uses less digits than its factorization.

28221520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2143 (or 2137 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 28221520 is about 5312.3930577471. The cubic root of 28221520 is about 304.4575865099.

The spelling of 28221520 in words is "twenty-eight million, two hundred twenty-one thousand, five hundred twenty".