81021600 has 432 divisors, whose sum is σ = 332478720. Its totient is φ = 19008000.

The previous prime is 81021583. The next prime is 81021623. The reversal of 81021600 is 612018.

It is a tau number, because it is divible by the number of its divisors (432).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 2613585 + ... + 2613615.

Almost surely, 2^81021600 is an apocalyptic number.

81021600 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 81021600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (166239360).

81021600 is an abundant number, since it is smaller than the sum of its proper divisors (251457120).

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

81021600 is a wasteful number, since it uses less digits than its factorization.

81021600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82 (or 52 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 81021600 is about 9001.1999200107. The cubic root of 81021600 is about 432.7133276626.

Adding to 81021600 its reverse (612018), we get a palindrome (81633618).

The spelling of 81021600 in words is "eighty-one million, twenty-one thousand, six hundred".