81471780 has 144 divisors (see below), whose sum is σ = 273624624. Its totient is φ = 19491840.

The previous prime is 81471763. The next prime is 81471857. The reversal of 81471780 is 8717418.

It can be written as a sum of positive squares in 8 ways, for example, as 39204 + 81432576 = 198^2 + 9024^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

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, 86110 + ... + 87050.

It is an arithmetic number, because the mean of its divisors is an integer number (1900171).

Almost surely, 2^81471780 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 81471780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (136812312).

81471780 is an abundant number, since it is smaller than the sum of its proper divisors (192152844).

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

81471780 is a wasteful number, since it uses less digits than its factorization.

81471780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1006 (or 1001 counting only the distinct ones).

The product of its (nonzero) digits is 12544, while the sum is 36.

The square root of 81471780 is about 9026.1719460688. The cubic root of 81471780 is about 433.5132756957.

The spelling of 81471780 in words is "eighty-one million, four hundred seventy-one thousand, seven hundred eighty".