81553 has 2 divisors, whose sum is σ = 81554. Its totient is φ = 81552.

The previous prime is 81551. The next prime is 81559. The reversal of 81553 is 35518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73984 + 7569 = 272^2 + 87^2 .

It is a cyclic number.

It is not a de Polignac number, because 81553 - 2¹ = 81551 is a prime.

Together with 81551, it forms a pair of twin primes.

81553 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40776 + 40777.

It is an arithmetic number, because the mean of its divisors is an integer number (40777).

2⁸¹⁵⁵³ is an apocalyptic number.

It is an amenable number.

81553 is a deficient number, since it is larger than the sum of its proper divisors (1).

81553 is an equidigital number, since it uses as much as digits as its factorization.

81553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 600, while the sum is 22.

The square root of 81553 is about 285.5748588374. The cubic root of 81553 is about 43.3657285701.

It can be divided in two parts, 815 and 53, that added together give a palindrome (868).

The spelling of 81553 in words is "eighty-one thousand, five hundred fifty-three".