28220557993 has 4 divisors (see below), whose sum is σ = 28263775428. Its totient is φ = 28177340560.

The previous prime is 28220557961. The next prime is 28220558077. The reversal of 28220557993 is 39975502282.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 39975502282 = 2 ⋅19987751141.

It can be written as a sum of positive squares in 2 ways, for example, as 14896934809 + 13323623184 = 122053^2 + 115428^2 .

It is a cyclic number.

It is not a de Polignac number, because 28220557993 - 2⁵ = 28220557961 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28220557993.

It is not an unprimeable number, because it can be changed into a prime (28220557943) 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, 21607738 + ... + 21609043.

It is an arithmetic number, because the mean of its divisors is an integer number (7065943857).

Almost surely, 2^28220557993 is an apocalyptic number.

It is an amenable number.

28220557993 is a deficient number, since it is larger than the sum of its proper divisors (43217435).

28220557993 is an equidigital number, since it uses as much as digits as its factorization.

28220557993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43217434.

The product of its (nonzero) digits is 2721600, while the sum is 52.

The spelling of 28220557993 in words is "twenty-eight billion, two hundred twenty million, five hundred fifty-seven thousand, nine hundred ninety-three".