81618839 has 2 divisors, whose sum is σ = 81618840. Its totient is φ = 81618838.

The previous prime is 81618821. The next prime is 81618841. The reversal of 81618839 is 93881618.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81618839 is a prime.

Together with 81618841, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81618839.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81618869) 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, 40809419 + 40809420.

It is an arithmetic number, because the mean of its divisors is an integer number (40809420).

Almost surely, 2^81618839 is an apocalyptic number.

81618839 is a deficient number, since it is larger than the sum of its proper divisors (1).

81618839 is an equidigital number, since it uses as much as digits as its factorization.

81618839 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82944, while the sum is 44.

The square root of 81618839 is about 9034.3145285074. The cubic root of 81618839 is about 433.7739537248.

The spelling of 81618839 in words is "eighty-one million, six hundred eighteen thousand, eight hundred thirty-nine".