78825781 has 2 divisors, whose sum is σ = 78825782. Its totient is φ = 78825780.

The previous prime is 78825779. The next prime is 78825809. The reversal of 78825781 is 18752887.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64883025 + 13942756 = 8055^2 + 3734^2 .

It is a cyclic number.

It is not a de Polignac number, because 78825781 - 2¹ = 78825779 is a prime.

It is a super-2 number, since 2×78825781² = 12427007500519922, which contains 22 as substring.

Together with 78825779, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78825731) by changing a digit.

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, 39412890 + 39412891.

It is an arithmetic number, because the mean of its divisors is an integer number (39412891).

Almost surely, 2^78825781 is an apocalyptic number.

It is an amenable number.

78825781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78825781 is an equidigital number, since it uses as much as digits as its factorization.

78825781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 250880, while the sum is 46.

The square root of 78825781 is about 8878.3884235823. The cubic root of 78825781 is about 428.7683903294.

It can be divided in two parts, 788 and 25781, that added together give a square (26569 = 163²).

The spelling of 78825781 in words is "seventy-eight million, eight hundred twenty-five thousand, seven hundred eighty-one".