81815535 has 16 divisors (see below), whose sum is σ = 145450080. Its totient is φ = 43634880.

The previous prime is 81815533. The next prime is 81815537. The reversal of 81815535 is 53551818.

It is an interprime number because it is at equal distance from previous prime (81815533) and next prime (81815537).

It is not a de Polignac number, because 81815535 - 2¹ = 81815533 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81815535.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81815533) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 302886 + ... + 303155.

It is an arithmetic number, because the mean of its divisors is an integer number (9090630).

Almost surely, 2^81815535 is an apocalyptic number.

81815535 is a deficient number, since it is larger than the sum of its proper divisors (63634545).

81815535 is a wasteful number, since it uses less digits than its factorization.

81815535 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 606055 (or 606049 counting only the distinct ones).

The product of its digits is 24000, while the sum is 36.

The square root of 81815535 is about 9045.1940277697. The cubic root of 81815535 is about 434.1221296870.

The spelling of 81815535 in words is "eighty-one million, eight hundred fifteen thousand, five hundred thirty-five".