81640170 has 64 divisors (see below), whose sum is σ = 221005440. Its totient is φ = 21441024.

The previous prime is 81640159. The next prime is 81640177. The reversal of 81640170 is 7104618.

It is a happy number.

81640170 is a `hidden beast` number, since 8 + 1 + 640 + 17 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (81640177) 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 31 ways as a sum of consecutive naturals, for example, 15834 + ... + 20346.

It is an arithmetic number, because the mean of its divisors is an integer number (3453210).

Almost surely, 2^81640170 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81640170, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (110502720).

81640170 is an abundant number, since it is smaller than the sum of its proper divisors (139365270).

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

81640170 is a wasteful number, since it uses less digits than its factorization.

81640170 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4596 (or 4590 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 81640170 is about 9035.4950058090. The cubic root of 81640170 is about 433.8117392261.

Adding to 81640170 its reverse (7104618), we get a palindrome (88744788).

It can be divided in two parts, 81640 and 170, that added together give a triangular number (81810 = T₄₀₄).

The spelling of 81640170 in words is "eighty-one million, six hundred forty thousand, one hundred seventy".