81805529 has 4 divisors (see below), whose sum is σ = 88098276. Its totient is φ = 75512784.

The previous prime is 81805519. The next prime is 81805541. The reversal of 81805529 is 92550818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 92550818 = 2 ⋅46275409.

It can be written as a sum of positive squares in 2 ways, for example, as 29214025 + 52591504 = 5405^2 + 7252^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81805529 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81805492 and 81805501.

It is not an unprimeable number, because it can be changed into a prime (81805519) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3146354 + ... + 3146379.

It is an arithmetic number, because the mean of its divisors is an integer number (22024569).

Almost surely, 2^81805529 is an apocalyptic number.

It is an amenable number.

81805529 is a deficient number, since it is larger than the sum of its proper divisors (6292747).

81805529 is a wasteful number, since it uses less digits than its factorization.

81805529 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6292746.

The product of its (nonzero) digits is 28800, while the sum is 38.

The square root of 81805529 is about 9044.6408994498. The cubic root of 81805529 is about 434.1044313240.

The spelling of 81805529 in words is "eighty-one million, eight hundred five thousand, five hundred twenty-nine".