81855047 has 2 divisors, whose sum is σ = 81855048. Its totient is φ = 81855046.

The previous prime is 81855043. The next prime is 81855073. The reversal of 81855047 is 74055818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81855047 - 2² = 81855043 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81855047.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81855043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40927523 + 40927524.

It is an arithmetic number, because the mean of its divisors is an integer number (40927524).

Almost surely, 2^81855047 is an apocalyptic number.

81855047 is a deficient number, since it is larger than the sum of its proper divisors (1).

81855047 is an equidigital number, since it uses as much as digits as its factorization.

81855047 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 44800, while the sum is 38.

The square root of 81855047 is about 9047.3779074382. The cubic root of 81855047 is about 434.1920034302.

The spelling of 81855047 in words is "eighty-one million, eight hundred fifty-five thousand, forty-seven".