81643266 has 24 divisors (see below), whose sum is σ = 186204720. Its totient is φ = 25781976.

The previous prime is 81643253. The next prime is 81643279. The reversal of 81643266 is 66234618.

81643266 is a `hidden beast` number, since 8 + 1 + 643 + 2 + 6 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (81643253) and next prime (81643279).

It is a self number, because there is not a number n which added to its sum of digits gives 81643266.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 119020 + ... + 119703.

It is an arithmetic number, because the mean of its divisors is an integer number (7758530).

Almost surely, 2^81643266 is an apocalyptic number.

81643266 is an abundant number, since it is smaller than the sum of its proper divisors (104561454).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81643266 is a wasteful number, since it uses less digits than its factorization.

81643266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 238750 (or 238747 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 81643266 is about 9035.6663285006. Note that the first 3 decimals coincide. The cubic root of 81643266 is about 433.8172228999.

The spelling of 81643266 in words is "eighty-one million, six hundred forty-three thousand, two hundred sixty-six".