81261600 has 216 divisors, whose sum is σ = 308136528. Its totient is φ = 18547200.

The previous prime is 81261589. The next prime is 81261617. The reversal of 81261600 is 616218.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 117255 + ... + 117945.

It is an arithmetic number, because the mean of its divisors is an integer number (1426558).

Almost surely, 2^81261600 is an apocalyptic number.

81261600 is a gapful number since it is divisible by the number (80) 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 81261600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (154068264).

81261600 is an abundant number, since it is smaller than the sum of its proper divisors (226874928).

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

81261600 is a wasteful number, since it uses less digits than its factorization.

81261600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 728 (or 708 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 81261600 is about 9014.5216179229. The cubic root of 81261600 is about 433.1401637381.

Adding to 81261600 its reverse (616218), we get a palindrome (81877818).

The spelling of 81261600 in words is "eighty-one million, two hundred sixty-one thousand, six hundred".