81806819 has 2 divisors, whose sum is σ = 81806820. Its totient is φ = 81806818.

The previous prime is 81806801. The next prime is 81806821. The reversal of 81806819 is 91860818.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81806819 - 2⁸ = 81806563 is a prime.

It is a super-2 number, since 2×81806819² = 13384711269797522, which contains 22 as substring.

Together with 81806821, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81800819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40903409 + 40903410.

It is an arithmetic number, because the mean of its divisors is an integer number (40903410).

Almost surely, 2^81806819 is an apocalyptic number.

81806819 is a deficient number, since it is larger than the sum of its proper divisors (1).

81806819 is an equidigital number, since it uses as much as digits as its factorization.

81806819 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27648, while the sum is 41.

The square root of 81806819 is about 9044.7122121160. The cubic root of 81806819 is about 434.1067131248.

The spelling of 81806819 in words is "eighty-one million, eight hundred six thousand, eight hundred nineteen".