28773781 has 2 divisors, whose sum is σ = 28773782. Its totient is φ = 28773780.

The previous prime is 28773779. The next prime is 28773793. The reversal of 28773781 is 18737782.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20702500 + 8071281 = 4550^2 + 2841^2 .

It is a cyclic number.

It is not a de Polignac number, because 28773781 - 2¹ = 28773779 is a prime.

It is a super-2 number, since 2×28773781² = 1655860946071922, which contains 22 as substring.

Together with 28773779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28773721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14386890 + 14386891.

It is an arithmetic number, because the mean of its divisors is an integer number (14386891).

Almost surely, 2^28773781 is an apocalyptic number.

It is an amenable number.

28773781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28773781 is an equidigital number, since it uses as much as digits as its factorization.

28773781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 131712, while the sum is 43.

The square root of 28773781 is about 5364.1197786776. The cubic root of 28773781 is about 306.4307268130.

The spelling of 28773781 in words is "twenty-eight million, seven hundred seventy-three thousand, seven hundred eighty-one".