81638400 has 132 divisors (see below), whose sum is σ = 270072992. Its totient is φ = 21749760.

The previous prime is 81638399. The next prime is 81638411. The reversal of 81638400 is 483618.

It is a happy number.

It is a super-3 number, since 3×81638400³ (a number of 25 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 76269 + ... + 77331.

Almost surely, 2^81638400 is an apocalyptic number.

81638400 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 81638400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (135036496).

81638400 is an abundant number, since it is smaller than the sum of its proper divisors (188434592).

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

81638400 is a wasteful number, since it uses less digits than its factorization.

81638400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1096 (or 1073 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 81638400 is about 9035.3970582371. The cubic root of 81638400 is about 433.8086041178.

The spelling of 81638400 in words is "eighty-one million, six hundred thirty-eight thousand, four hundred".