81943680 has 384 divisors, whose sum is σ = 332095680. Its totient is φ = 17031168.

The previous prime is 81943669. The next prime is 81943717. The reversal of 81943680 is 8634918.

81943680 = 42² + 43² + ... + 626².

It is a tau number, because it is divible by the number of its divisors (384).

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1223007 + ... + 1223073.

Almost surely, 2^81943680 is an apocalyptic number.

81943680 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 81943680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (166047840).

81943680 is an abundant number, since it is smaller than the sum of its proper divisors (250152000).

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

81943680 is a wasteful number, since it uses less digits than its factorization.

81943680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116 (or 97 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 39.

The square root of 81943680 is about 9052.2748522126. The cubic root of 81943680 is about 434.3486618953.

The spelling of 81943680 in words is "eighty-one million, nine hundred forty-three thousand, six hundred eighty".