81631680 has 224 divisors, whose sum is σ = 289486848. Its totient is φ = 19353600.

The previous prime is 81631651. The next prime is 81631687. The reversal of 81631680 is 8613618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81631687) by changing a digit.

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, 386775 + ... + 386985.

It is an arithmetic number, because the mean of its divisors is an integer number (1292352).

Almost surely, 2^81631680 is an apocalyptic number.

81631680 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 81631680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144743424).

81631680 is an abundant number, since it is smaller than the sum of its proper divisors (207855168).

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

81631680 is a wasteful number, since it uses less digits than its factorization.

81631680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275 (or 265 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 81631680 is about 9035.0251798210. The cubic root of 81631680 is about 433.7967009211.

The spelling of 81631680 in words is "eighty-one million, six hundred thirty-one thousand, six hundred eighty".