81644155 has 8 divisors (see below), whose sum is σ = 98027712. Its totient is φ = 65278848.

The previous prime is 81644153. The next prime is 81644177. The reversal of 81644155 is 55144618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81644155 - 2¹ = 81644153 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81644155.

It is not an unprimeable number, because it can be changed into a prime (81644153) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8899 + ... + 15571.

It is an arithmetic number, because the mean of its divisors is an integer number (12253464).

Almost surely, 2^81644155 is an apocalyptic number.

81644155 is a deficient number, since it is larger than the sum of its proper divisors (16383557).

81644155 is a wasteful number, since it uses less digits than its factorization.

81644155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9125.

The product of its digits is 19200, while the sum is 34.

The square root of 81644155 is about 9035.7155223037. The cubic root of 81644155 is about 433.8187974821.

The spelling of 81644155 in words is "eighty-one million, six hundred forty-four thousand, one hundred fifty-five".