81601635600 has 525 divisors, whose sum is σ = 307298175253. Its totient is φ = 20814330240.

The previous prime is 81601635589. The next prime is 81601635673. The reversal of 81601635600 is 653610618.

It is a happy number.

The square root of 81601635600 is 285660.

It is a perfect power (a square), and thus also a powerful number.

81601635600 is a `hidden beast` number, since 8 + 1 + 6 + 0 + 16 + 35 + 600 = 666.

It can be written as a sum of positive squares in only one way, i.e., 29376588816 + 52225046784 = 171396^2 + 228528^2 .

It is a super-3 number, since 3×81601635600³ (a number of 34 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 104 ways as a sum of consecutive naturals, for example, 3547897189 + ... + 3547897211.

Almost surely, 2^81601635600 is an apocalyptic number.

81601635600 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

81601635600 is the 285660-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81601635600

81601635600 is an abundant number, since it is smaller than the sum of its proper divisors (225696539653).

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

81601635600 is an frugal number, since it uses more digits than its factorization.

81601635600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128 (or 33 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

Multiplying 81601635600 by its sum of digits (36), we get a square (2937658881600 = 1713960²).

81601635600 divided by its sum of digits (36) gives a square (2266712100 = 47610²).

The spelling of 81601635600 in words is "eighty-one billion, six hundred one million, six hundred thirty-five thousand, six hundred".