28077781 has 2 divisors, whose sum is σ = 28077782. Its totient is φ = 28077780.

The previous prime is 28077773. The next prime is 28077787. The reversal of 28077781 is 18777082.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23912100 + 4165681 = 4890^2 + 2041^2 .

It is a cyclic number.

It is not a de Polignac number, because 28077781 - 2³ = 28077773 is a prime.

It is a super-2 number, since 2×28077781² = 1576723571767922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28077787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14038890 + 14038891.

It is an arithmetic number, because the mean of its divisors is an integer number (14038891).

Almost surely, 2^28077781 is an apocalyptic number.

It is an amenable number.

28077781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28077781 is an equidigital number, since it uses as much as digits as its factorization.

28077781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43904, while the sum is 40.

The square root of 28077781 is about 5298.8471387652. The cubic root of 28077781 is about 303.9398145223.

The spelling of 28077781 in words is "twenty-eight million, seventy-seven thousand, seven hundred eighty-one".