78879781 has 2 divisors, whose sum is σ = 78879782. Its totient is φ = 78879780.

The previous prime is 78879743. The next prime is 78879803. The reversal of 78879781 is 18797887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 67387681 + 11492100 = 8209^2 + 3390^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78879781 is a prime.

It is a super-2 number, since 2×78879781² = 12444039701215922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78849781) 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, 39439890 + 39439891.

It is an arithmetic number, because the mean of its divisors is an integer number (39439891).

Almost surely, 2^78879781 is an apocalyptic number.

It is an amenable number.

78879781 is a deficient number, since it is larger than the sum of its proper divisors (1).

78879781 is an equidigital number, since it uses as much as digits as its factorization.

78879781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1580544, while the sum is 55.

The square root of 78879781 is about 8881.4289953813. The cubic root of 78879781 is about 428.8662779649.

It can be divided in two parts, 7 and 8879781, that added together give a palindrome (8879788).

The spelling of 78879781 in words is "seventy-eight million, eight hundred seventy-nine thousand, seven hundred eighty-one".