81621 has 8 divisors (see below), whose sum is σ = 120960. Its totient is φ = 54396.

The previous prime is 81619. The next prime is 81629. The reversal of 81621 is 12618.

It is not a de Polignac number, because 81621 - 2¹ = 81619 is a prime.

It is a Curzon number.

81621 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 81594 and 81603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1485 + ... + 1538.

It is an arithmetic number, because the mean of its divisors is an integer number (15120).

2⁸¹⁶²¹ is an apocalyptic number.

It is an amenable number.

81621 is a deficient number, since it is larger than the sum of its proper divisors (39339).

81621 is a wasteful number, since it uses less digits than its factorization.

81621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3032 (or 3026 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

The square root of 81621 is about 285.6938921293. The cubic root of 81621 is about 43.3777781996.

The spelling of 81621 in words is "eighty-one thousand, six hundred twenty-one".