81533 has 2 divisors, whose sum is σ = 81534. Its totient is φ = 81532.

The previous prime is 81527. The next prime is 81547. The reversal of 81533 is 33518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80089 + 1444 = 283^2 + 38^2 .

It is a cyclic number.

It is not a de Polignac number, because 81533 - 2⁴ = 81517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40766 + 40767.

It is an arithmetic number, because the mean of its divisors is an integer number (40767).

2⁸¹⁵³³ is an apocalyptic number.

It is an amenable number.

81533 is a deficient number, since it is larger than the sum of its proper divisors (1).

81533 is an equidigital number, since it uses as much as digits as its factorization.

81533 is an evil number, because the sum of its binary digits is even.

The product of its digits is 360, while the sum is 20.

The square root of 81533 is about 285.5398396021. The cubic root of 81533 is about 43.3621832867.

It can be divided in two parts, 815 and 33, that added together give a palindrome (848).

The spelling of 81533 in words is "eighty-one thousand, five hundred thirty-three".