81855510 has 64 divisors (see below), whose sum is σ = 226934784. Its totient is φ = 18675200.

The previous prime is 81855491. The next prime is 81855517. The reversal of 81855510 is 1555818.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81855517) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1686 + ... + 12905.

It is an arithmetic number, because the mean of its divisors is an integer number (3545856).

Almost surely, 2^81855510 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81855510, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113467392).

81855510 is an abundant number, since it is smaller than the sum of its proper divisors (145079274).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81855510 is a wasteful number, since it uses less digits than its factorization.

81855510 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14629.

The product of its (nonzero) digits is 8000, while the sum is 33.

The square root of 81855510 is about 9047.4034949260. The cubic root of 81855510 is about 434.1928220745.

It can be divided in two parts, 8185 and 5510, that added together give a triangular number (13695 = T₁₆₅).

The spelling of 81855510 in words is "eighty-one million, eight hundred fifty-five thousand, five hundred ten".