28720344781 has 2 divisors, whose sum is σ = 28720344782. Its totient is φ = 28720344780.

The previous prime is 28720344739. The next prime is 28720344811. The reversal of 28720344781 is 18744302782.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28442822500 + 277522281 = 168650^2 + 16659^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28720344781 is a prime.

It is a super-2 number, since 2×28720344781² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28720344701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14360172390 + 14360172391.

It is an arithmetic number, because the mean of its divisors is an integer number (14360172391).

Almost surely, 2^28720344781 is an apocalyptic number.

It is an amenable number.

28720344781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28720344781 is an equidigital number, since it uses as much as digits as its factorization.

28720344781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 602112, while the sum is 46.

The spelling of 28720344781 in words is "twenty-eight billion, seven hundred twenty million, three hundred forty-four thousand, seven hundred eighty-one".