20728750557 has 4 divisors (see below), whose sum is σ = 27638334080. Its totient is φ = 13819167036.

The previous prime is 20728750517. The next prime is 20728750561. The reversal of 20728750557 is 75505782702.

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 not a de Polignac number, because 20728750557 - 2¹⁸ = 20728488413 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 (20728750517) 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, 3454791757 + ... + 3454791762.

It is an arithmetic number, because the mean of its divisors is an integer number (6909583520).

Almost surely, 2^20728750557 is an apocalyptic number.

It is an amenable number.

20728750557 is a deficient number, since it is larger than the sum of its proper divisors (6909583523).

20728750557 is an equidigital number, since it uses as much as digits as its factorization.

20728750557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6909583522.

The product of its (nonzero) digits is 1372000, while the sum is 48.

The spelling of 20728750557 in words is "twenty billion, seven hundred twenty-eight million, seven hundred fifty thousand, five hundred fifty-seven".