81646 has 4 divisors (see below), whose sum is σ = 122472. Its totient is φ = 40822.

The previous prime is 81637. The next prime is 81647. The reversal of 81646 is 64618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 64618 = 2 ⋅32309.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 81646.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20410 + ... + 20413.

It is an arithmetic number, because the mean of its divisors is an integer number (30618).

2⁸¹⁶⁴⁶ is an apocalyptic number.

81646 is a deficient number, since it is larger than the sum of its proper divisors (40826).

81646 is a wasteful number, since it uses less digits than its factorization.

81646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40825.

The product of its digits is 1152, while the sum is 25.

The square root of 81646 is about 285.7376419025. The cubic root of 81646 is about 43.3822065279.

It can be divided in two parts, 8164 and 6, that multiplied together give a palindrome (48984).

The spelling of 81646 in words is "eighty-one thousand, six hundred forty-six".