28681381 has 2 divisors, whose sum is σ = 28681382. Its totient is φ = 28681380.

The previous prime is 28681379. The next prime is 28681403. The reversal of 28681381 is 18318682.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27730756 + 950625 = 5266^2 + 975^2 .

It is a cyclic number.

It is not a de Polignac number, because 28681381 - 2¹ = 28681379 is a prime.

It is a super-2 number, since 2×28681381² = 1645243232134322, which contains 22 as substring.

Together with 28681379, it forms a pair of twin primes.

It is a Chen prime.

It is the 5356-th Hogben number.

It is a self number, because there is not a number n which added to its sum of digits gives 28681381.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28681351) by changing a digit.

It is a nontrivial repunit in base 5355.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14340690 + 14340691.

It is an arithmetic number, because the mean of its divisors is an integer number (14340691).

Almost surely, 2^28681381 is an apocalyptic number.

It is an amenable number.

28681381 is a deficient number, since it is larger than the sum of its proper divisors (1).

28681381 is an equidigital number, since it uses as much as digits as its factorization.

28681381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18432, while the sum is 37.

The square root of 28681381 is about 5355.5000700215. The cubic root of 28681381 is about 306.1023658259.

The spelling of 28681381 in words is "twenty-eight million, six hundred eighty-one thousand, three hundred eighty-one".