81858613 has 2 divisors, whose sum is σ = 81858614. Its totient is φ = 81858612.

The previous prime is 81858611. The next prime is 81858641. The reversal of 81858613 is 31685818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81848209 + 10404 = 9047^2 + 102^2 .

It is a cyclic number.

It is not a de Polignac number, because 81858613 - 2¹ = 81858611 is a prime.

Together with 81858611, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81858611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40929306 + 40929307.

It is an arithmetic number, because the mean of its divisors is an integer number (40929307).

Almost surely, 2^81858613 is an apocalyptic number.

It is an amenable number.

81858613 is a deficient number, since it is larger than the sum of its proper divisors (1).

81858613 is an equidigital number, since it uses as much as digits as its factorization.

81858613 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46080, while the sum is 40.

The square root of 81858613 is about 9047.5749789654. The cubic root of 81858613 is about 434.1983085034.

The spelling of 81858613 in words is "eighty-one million, eight hundred fifty-eight thousand, six hundred thirteen".