28220121 has 12 divisors (see below), whose sum is σ = 41321748. Its totient is φ = 18555264.

The previous prime is 28220089. The next prime is 28220123. The reversal of 28220121 is 12102282.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 7617600 + 20602521 = 2760^2 + 4539^2 .

It is not a de Polignac number, because 28220121 - 2⁵ = 28220089 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 28220094 and 28220103.

It is not an unprimeable number, because it can be changed into a prime (28220123) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 20820 + ... + 22133.

It is an arithmetic number, because the mean of its divisors is an integer number (3443479).

Almost surely, 2^28220121 is an apocalyptic number.

It is an amenable number.

28220121 is a deficient number, since it is larger than the sum of its proper divisors (13101627).

28220121 is a wasteful number, since it uses less digits than its factorization.

28220121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43032 (or 43029 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 28220121 is about 5312.2613828764. The cubic root of 28220121 is about 304.4525555595.

The spelling of 28220121 in words is "twenty-eight million, two hundred twenty thousand, one hundred twenty-one".