81163644 has 48 divisors (see below), whose sum is σ = 205960608. Its totient is φ = 24772608.

The previous prime is 81163633. The next prime is 81163697. The reversal of 81163644 is 44636118.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2172 + ... + 12924.

It is an arithmetic number, because the mean of its divisors is an integer number (4290846).

Almost surely, 2^81163644 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 81163644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102980304).

81163644 is an abundant number, since it is smaller than the sum of its proper divisors (124796964).

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

81163644 is a wasteful number, since it uses less digits than its factorization.

81163644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10814 (or 10812 counting only the distinct ones).

The product of its digits is 13824, while the sum is 33.

The square root of 81163644 is about 9009.0867461691. The cubic root of 81163644 is about 432.9660522360.

The spelling of 81163644 in words is "eighty-one million, one hundred sixty-three thousand, six hundred forty-four".