84778781 has 2 divisors, whose sum is σ = 84778782. Its totient is φ = 84778780.

The previous prime is 84778721. The next prime is 84778787. The reversal of 84778781 is 18787748.

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., 45778756 + 39000025 = 6766^2 + 6245^2 .

It is a cyclic number.

It is not a de Polignac number, because 84778781 - 2⁶ = 84778717 is a prime.

It is a super-2 number, since 2×84778781² = 14374883415691922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (84778787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42389390 + 42389391.

It is an arithmetic number, because the mean of its divisors is an integer number (42389391).

Almost surely, 2^84778781 is an apocalyptic number.

It is an amenable number.

84778781 is a deficient number, since it is larger than the sum of its proper divisors (1).

84778781 is an equidigital number, since it uses as much as digits as its factorization.

84778781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 702464, while the sum is 50.

The square root of 84778781 is about 9207.5393564187. The cubic root of 84778781 is about 439.3011996493.

The spelling of 84778781 in words is "eighty-four million, seven hundred seventy-eight thousand, seven hundred eighty-one".