81618239 has 2 divisors, whose sum is σ = 81618240. Its totient is φ = 81618238.

The previous prime is 81618233. The next prime is 81618253. The reversal of 81618239 is 93281618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81618239 - 2⁸ = 81617983 is a prime.

It is a super-2 number, since 2×81618239² = 13323073874922242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81618233) 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, 40809119 + 40809120.

It is an arithmetic number, because the mean of its divisors is an integer number (40809120).

Almost surely, 2^81618239 is an apocalyptic number.

81618239 is a deficient number, since it is larger than the sum of its proper divisors (1).

81618239 is an equidigital number, since it uses as much as digits as its factorization.

81618239 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 38.

The square root of 81618239 is about 9034.2813217212. The cubic root of 81618239 is about 433.7728907961.

The spelling of 81618239 in words is "eighty-one million, six hundred eighteen thousand, two hundred thirty-nine".