81420439 has 2 divisors, whose sum is σ = 81420440. Its totient is φ = 81420438.

The previous prime is 81420431. The next prime is 81420503. The reversal of 81420439 is 93402418.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81420439 - 2³ = 81420431 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81420439.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81420431) 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, 40710219 + 40710220.

It is an arithmetic number, because the mean of its divisors is an integer number (40710220).

Almost surely, 2^81420439 is an apocalyptic number.

81420439 is a deficient number, since it is larger than the sum of its proper divisors (1).

81420439 is an equidigital number, since it uses as much as digits as its factorization.

81420439 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 81420439 is about 9023.3274904549. The cubic root of 81420439 is about 433.4221943341.

The spelling of 81420439 in words is "eighty-one million, four hundred twenty thousand, four hundred thirty-nine".