81249979 has 2 divisors, whose sum is σ = 81249980. Its totient is φ = 81249978.

The previous prime is 81249943. The next prime is 81249997. The reversal of 81249979 is 97994218.

Together with next prime (81249997) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81249979 - 2¹⁹ = 80725691 is a prime.

It is not a weakly prime, because it can be changed into another prime (81243979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40624989 + 40624990.

It is an arithmetic number, because the mean of its divisors is an integer number (40624990).

Almost surely, 2^81249979 is an apocalyptic number.

81249979 is a deficient number, since it is larger than the sum of its proper divisors (1).

81249979 is an equidigital number, since it uses as much as digits as its factorization.

81249979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 49.

The square root of 81249979 is about 9013.8770237895. The cubic root of 81249979 is about 433.1195153555.

It can be divided in two parts, 81249 and 979, that added together give a palindrome (82228).

The spelling of 81249979 in words is "eighty-one million, two hundred forty-nine thousand, nine hundred seventy-nine".