81211387 has 2 divisors, whose sum is σ = 81211388. Its totient is φ = 81211386.

The previous prime is 81211379. The next prime is 81211393. The reversal of 81211387 is 78311218.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81211387 - 2³ = 81211379 is a prime.

It is not a weakly prime, because it can be changed into another prime (81211307) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40605693 + 40605694.

It is an arithmetic number, because the mean of its divisors is an integer number (40605694).

Almost surely, 2^81211387 is an apocalyptic number.

81211387 is a deficient number, since it is larger than the sum of its proper divisors (1).

81211387 is an equidigital number, since it uses as much as digits as its factorization.

81211387 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 31.

The square root of 81211387 is about 9011.7360702586. The cubic root of 81211387 is about 433.0509303308.

The spelling of 81211387 in words is "eighty-one million, two hundred eleven thousand, three hundred eighty-seven".