81651800 has 48 divisors (see below), whose sum is σ = 193447440. Its totient is φ = 32040320.

The previous prime is 81651767. The next prime is 81651809. The reversal of 81651800 is 815618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81651809) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6749 + ... + 14451.

It is an arithmetic number, because the mean of its divisors is an integer number (4030155).

Almost surely, 2^81651800 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81651800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96723720).

81651800 is an abundant number, since it is smaller than the sum of its proper divisors (111795640).

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

81651800 is a wasteful number, since it uses less digits than its factorization.

81651800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7772 (or 7763 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 29.

The square root of 81651800 is about 9036.1385558213. The cubic root of 81651800 is about 433.8323377092.

The spelling of 81651800 in words is "eighty-one million, six hundred fifty-one thousand, eight hundred".