81632640 has 256 divisors, whose sum is σ = 286856640. Its totient is φ = 19660800.

The previous prime is 81632633. The next prime is 81632653. The reversal of 81632640 is 4623618.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

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

It is a junction number, because it is equal to n+sod(n) for n = 81632598 and 81632607.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 1338210 + ... + 1338270.

Almost surely, 2^81632640 is an apocalyptic number.

81632640 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 81632640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (143428320).

81632640 is an abundant number, since it is smaller than the sum of its proper divisors (205224000).

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

81632640 is a wasteful number, since it uses less digits than its factorization.

81632640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141 (or 129 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 81632640 is about 9035.0783062462. The cubic root of 81632640 is about 433.7984014177.

The spelling of 81632640 in words is "eighty-one million, six hundred thirty-two thousand, six hundred forty".