81509208 has 64 divisors (see below), whose sum is σ = 226108800. Its totient is φ = 24276480.

The previous prime is 81509191. The next prime is 81509231. The reversal of 81509208 is 80290518.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12960 + ... + 18192.

It is an arithmetic number, because the mean of its divisors is an integer number (3532950).

Almost surely, 2^81509208 is an apocalyptic number.

81509208 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81509208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113054400).

81509208 is an abundant number, since it is smaller than the sum of its proper divisors (144599592).

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

81509208 is a wasteful number, since it uses less digits than its factorization.

81509208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5312 (or 5308 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 33.

The square root of 81509208 is about 9028.2450121826. The cubic root of 81509208 is about 433.5796506247.

The spelling of 81509208 in words is "eighty-one million, five hundred nine thousand, two hundred eight".