81385205 has 48 divisors (see below), whose sum is σ = 117037872. Its totient is φ = 54067200.

The previous prime is 81385193. The next prime is 81385253. The reversal of 81385205 is 50258318.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 9084196 + 72301009 = 3014^2 + 8503^2 .

It is not a de Polignac number, because 81385205 - 2¹⁸ = 81123061 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 in 47 ways as a sum of consecutive naturals, for example, 421589 + ... + 421781.

It is an arithmetic number, because the mean of its divisors is an integer number (2438289).

Almost surely, 2^81385205 is an apocalyptic number.

81385205 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81385205 is a deficient number, since it is larger than the sum of its proper divisors (35652667).

81385205 is a wasteful number, since it uses less digits than its factorization.

81385205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278 (or 267 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 32.

The square root of 81385205 is about 9021.3748952141. The cubic root of 81385205 is about 433.3596653953.

The spelling of 81385205 in words is "eighty-one million, three hundred eighty-five thousand, two hundred five".