28121810 has 8 divisors (see below), whose sum is σ = 50619276. Its totient is φ = 11248720.

The previous prime is 28121803. The next prime is 28121827. The reversal of 28121810 is 1812182.

It is a happy number.

It is a Cunningham number, because it is equal to 5303²+1.

It can be written as a sum of positive squares in 2 ways, for example, as 28121809 + 1 = 5303^2 + 1^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×28121810² = 1581672395352200, which contains 22 as substring.

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 3 ways as a sum of consecutive naturals, for example, 1406081 + ... + 1406100.

Almost surely, 2^28121810 is an apocalyptic number.

28121810 is a deficient number, since it is larger than the sum of its proper divisors (22497466).

28121810 is a wasteful number, since it uses less digits than its factorization.

28121810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2812188.

The product of its (nonzero) digits is 256, while the sum is 23.

The square root of 28121810 is about 5303.0000942863. Note that the first 4 decimals coincide. The cubic root of 28121810 is about 304.0986017295.

Adding to 28121810 its reverse (1812182), we get a palindrome (29933992).

The spelling of 28121810 in words is "twenty-eight million, one hundred twenty-one thousand, eight hundred ten".