81947880 has 192 divisors, whose sum is σ = 314496000. Its totient is φ = 18109440.

The previous prime is 81947861. The next prime is 81947897. The reversal of 81947880 is 8874918.

It is a Harshad number since it is a multiple of its sum of digits (45).

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 47 ways as a sum of consecutive naturals, for example, 77596 + ... + 78644.

It is an arithmetic number, because the mean of its divisors is an integer number (1638000).

Almost surely, 2^81947880 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81947880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (157248000).

81947880 is an abundant number, since it is smaller than the sum of its proper divisors (232548120).

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

81947880 is a wasteful number, since it uses less digits than its factorization.

81947880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1104 (or 1097 counting only the distinct ones).

The product of its (nonzero) digits is 129024, while the sum is 45.

The square root of 81947880 is about 9052.5068351258. The cubic root of 81947880 is about 434.3560825742.

The spelling of 81947880 in words is "eighty-one million, nine hundred forty-seven thousand, eight hundred eighty".