81667213 has 2 divisors, whose sum is σ = 81667214. Its totient is φ = 81667212.

The previous prime is 81667193. The next prime is 81667241. The reversal of 81667213 is 31276618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69255684 + 12411529 = 8322^2 + 3523^2 .

It is a cyclic number.

It is not a de Polignac number, because 81667213 - 2⁹ = 81666701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81667513) 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, 40833606 + 40833607.

It is an arithmetic number, because the mean of its divisors is an integer number (40833607).

Almost surely, 2^81667213 is an apocalyptic number.

It is an amenable number.

81667213 is a deficient number, since it is larger than the sum of its proper divisors (1).

81667213 is an equidigital number, since it uses as much as digits as its factorization.

81667213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 34.

The square root of 81667213 is about 9036.9913688130. The cubic root of 81667213 is about 433.8596334419.

The spelling of 81667213 in words is "eighty-one million, six hundred sixty-seven thousand, two hundred thirteen".