81655807 has 2 divisors, whose sum is σ = 81655808. Its totient is φ = 81655806.

The previous prime is 81655799. The next prime is 81655813. The reversal of 81655807 is 70855618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81655807 - 2³ = 81655799 is a prime.

It is a super-3 number, since 3×81655807³ (a number of 25 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81655807.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81656807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40827903 + 40827904.

It is an arithmetic number, because the mean of its divisors is an integer number (40827904).

Almost surely, 2^81655807 is an apocalyptic number.

81655807 is a deficient number, since it is larger than the sum of its proper divisors (1).

81655807 is an equidigital number, since it uses as much as digits as its factorization.

81655807 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 67200, while the sum is 40.

The square root of 81655807 is about 9036.3602739156. The cubic root of 81655807 is about 433.8394342571.

The spelling of 81655807 in words is "eighty-one million, six hundred fifty-five thousand, eight hundred seven".