81818623 has 2 divisors, whose sum is σ = 81818624. Its totient is φ = 81818622.

The previous prime is 81818621. The next prime is 81818687. The reversal of 81818623 is 32681818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81818623 - 2¹ = 81818621 is a prime.

It is a super-2 number, since 2×81818623² = 13388574139232258, which contains 22 as substring.

Together with 81818621, 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 (81818621) 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, 40909311 + 40909312.

It is an arithmetic number, because the mean of its divisors is an integer number (40909312).

Almost surely, 2^81818623 is an apocalyptic number.

81818623 is a deficient number, since it is larger than the sum of its proper divisors (1).

81818623 is an equidigital number, since it uses as much as digits as its factorization.

81818623 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18432, while the sum is 37.

The square root of 81818623 is about 9045.3647245426. The cubic root of 81818623 is about 434.1275913730.

The spelling of 81818623 in words is "eighty-one million, eight hundred eighteen thousand, six hundred twenty-three".