81604279 has 2 divisors, whose sum is σ = 81604280. Its totient is φ = 81604278.

The previous prime is 81604261. The next prime is 81604321. The reversal of 81604279 is 97240618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81604279 - 2⁷ = 81604151 is a prime.

It is a super-2 number, since 2×81604279² = 13318516702219682, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81604249) 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, 40802139 + 40802140.

It is an arithmetic number, because the mean of its divisors is an integer number (40802140).

Almost surely, 2^81604279 is an apocalyptic number.

81604279 is a deficient number, since it is larger than the sum of its proper divisors (1).

81604279 is an equidigital number, since it uses as much as digits as its factorization.

81604279 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 81604279 is about 9033.5086760350. The cubic root of 81604279 is about 433.7481585185.

The spelling of 81604279 in words is "eighty-one million, six hundred four thousand, two hundred seventy-nine".