81664143 has 16 divisors (see below), whose sum is σ = 121996416. Its totient is φ = 48155040.

The previous prime is 81664139. The next prime is 81664153. The reversal of 81664143 is 34146618.

It is not a de Polignac number, because 81664143 - 2² = 81664139 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81664153) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32221 + ... + 34662.

It is an arithmetic number, because the mean of its divisors is an integer number (7624776).

Almost surely, 2^81664143 is an apocalyptic number.

81664143 is a deficient number, since it is larger than the sum of its proper divisors (40332273).

81664143 is a wasteful number, since it uses less digits than its factorization.

81664143 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66934.

The product of its digits is 13824, while the sum is 33.

The square root of 81664143 is about 9036.8215098009. The cubic root of 81664143 is about 433.8541968833.

The spelling of 81664143 in words is "eighty-one million, six hundred sixty-four thousand, one hundred forty-three".