28312121381 has 2 divisors, whose sum is σ = 28312121382. Its totient is φ = 28312121380.

The previous prime is 28312121359. The next prime is 28312121389. The reversal of 28312121381 is 18312121382.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19996505281 + 8315616100 = 141409^2 + 91190^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28312121381 is a prime.

It is a super-3 number, since 3×28312121381³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28312121389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14156060690 + 14156060691.

It is an arithmetic number, because the mean of its divisors is an integer number (14156060691).

Almost surely, 2^28312121381 is an apocalyptic number.

It is an amenable number.

28312121381 is a deficient number, since it is larger than the sum of its proper divisors (1).

28312121381 is an equidigital number, since it uses as much as digits as its factorization.

28312121381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4608, while the sum is 32.

Subtracting from 28312121381 its reverse (18312121382), we obtain a palindrome (9999999999).

It can be divided in two parts, 2831 and 2121381, that added together give a palindrome (2124212).

The spelling of 28312121381 in words is "twenty-eight billion, three hundred twelve million, one hundred twenty-one thousand, three hundred eighty-one".