81555533 has 2 divisors, whose sum is σ = 81555534. Its totient is φ = 81555532.

The previous prime is 81555517. The next prime is 81555547. The reversal of 81555533 is 33555518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78180964 + 3374569 = 8842^2 + 1837^2 .

It is a cyclic number.

It is not a de Polignac number, because 81555533 - 2⁴ = 81555517 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81555493 and 81555502.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81555233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40777766 + 40777767.

It is an arithmetic number, because the mean of its divisors is an integer number (40777767).

Almost surely, 2^81555533 is an apocalyptic number.

It is an amenable number.

81555533 is a deficient number, since it is larger than the sum of its proper divisors (1).

81555533 is an equidigital number, since it uses as much as digits as its factorization.

81555533 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45000, while the sum is 35.

The square root of 81555533 is about 9030.8102072848. The cubic root of 81555533 is about 433.6617753885.

The spelling of 81555533 in words is "eighty-one million, five hundred fifty-five thousand, five hundred thirty-three".