81205211 has 2 divisors, whose sum is σ = 81205212. Its totient is φ = 81205210.

The previous prime is 81205207. The next prime is 81205231. The reversal of 81205211 is 11250218.

It is a happy number.

It is an a-pointer prime, because the next prime (81205231) can be obtained adding 81205211 to its sum of digits (20).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81205211 - 2² = 81205207 is a prime.

It is not a weakly prime, because it can be changed into another prime (81205231) 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, 40602605 + 40602606.

It is an arithmetic number, because the mean of its divisors is an integer number (40602606).

Almost surely, 2^81205211 is an apocalyptic number.

81205211 is a deficient number, since it is larger than the sum of its proper divisors (1).

81205211 is an equidigital number, since it uses as much as digits as its factorization.

81205211 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 81205211 is about 9011.3933994694. The cubic root of 81205211 is about 433.0399524354.

Adding to 81205211 its reverse (11250218), we get a palindrome (92455429).

It can be divided in two parts, 8120 and 5211, that added together give a palindrome (13331).

The spelling of 81205211 in words is "eighty-one million, two hundred five thousand, two hundred eleven".