28355715221 has 4 divisors (see below), whose sum is σ = 29270415744. Its totient is φ = 27441014700.

The previous prime is 28355715061. The next prime is 28355715239. The reversal of 28355715221 is 12251755382.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28355715221 - 2¹⁴ = 28355698837 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 (28355715281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 457350215 + ... + 457350276.

It is an arithmetic number, because the mean of its divisors is an integer number (7317603936).

Almost surely, 2^28355715221 is an apocalyptic number.

It is an amenable number.

28355715221 is a deficient number, since it is larger than the sum of its proper divisors (914700523).

28355715221 is an equidigital number, since it uses as much as digits as its factorization.

28355715221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 914700522.

The product of its digits is 168000, while the sum is 41.

The spelling of 28355715221 in words is "twenty-eight billion, three hundred fifty-five million, seven hundred fifteen thousand, two hundred twenty-one".