28910211221 has 4 divisors (see below), whose sum is σ = 28910622444. Its totient is φ = 28909800000.

The previous prime is 28910211049. The next prime is 28910211227. The reversal of 28910211221 is 12211201982.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15404284996 + 13505926225 = 124114^2 + 116215^2 .

It is a cyclic number.

It is not a de Polignac number, because 28910211221 - 2¹⁴ = 28910194837 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28910211227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70610 + ... + 250611.

It is an arithmetic number, because the mean of its divisors is an integer number (7227655611).

Almost surely, 2^28910211221 is an apocalyptic number.

It is an amenable number.

28910211221 is a deficient number, since it is larger than the sum of its proper divisors (411223).

28910211221 is an equidigital number, since it uses as much as digits as its factorization.

28910211221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 411222.

The product of its (nonzero) digits is 1152, while the sum is 29.

The spelling of 28910211221 in words is "twenty-eight billion, nine hundred ten million, two hundred eleven thousand, two hundred twenty-one".