81663444 has 96 divisors (see below), whose sum is σ = 236073600. Its totient is φ = 24261120.

The previous prime is 81663443. The next prime is 81663479. The reversal of 81663444 is 44436618.

81663444 is a `hidden beast` number, since 8 + 16 + 634 + 4 + 4 = 666.

It is a super-2 number, since 2×81663444² = 13337836171882272, which contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 81663399 and 81663408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81663443) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 33714 + ... + 36054.

It is an arithmetic number, because the mean of its divisors is an integer number (2459100).

Almost surely, 2^81663444 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 81663444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118036800).

81663444 is an abundant number, since it is smaller than the sum of its proper divisors (154410156).

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

81663444 is a wasteful number, since it uses less digits than its factorization.

81663444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2390 (or 2382 counting only the distinct ones).

The product of its digits is 55296, while the sum is 36.

The square root of 81663444 is about 9036.7828346154. The cubic root of 81663444 is about 433.8529590290.

The spelling of 81663444 in words is "eighty-one million, six hundred sixty-three thousand, four hundred forty-four".