81644472 has 192 divisors, whose sum is σ = 288550080. Its totient is φ = 20238336.

The previous prime is 81644471. The next prime is 81644473. The reversal of 81644472 is 27444618.

81644472 is a `hidden beast` number, since 8 + 1 + 644 + 4 + 7 + 2 = 666.

It is an interprime number because it is at equal distance from previous prime (81644471) and next prime (81644473).

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81644471) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 111018 + ... + 111750.

It is an arithmetic number, because the mean of its divisors is an integer number (1502865).

Almost surely, 2^81644472 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 81644472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144275040).

81644472 is an abundant number, since it is smaller than the sum of its proper divisors (206905608).

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

81644472 is a wasteful number, since it uses less digits than its factorization.

81644472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 782 (or 775 counting only the distinct ones).

The product of its digits is 43008, while the sum is 36.

The square root of 81644472 is about 9035.7330637862. The cubic root of 81644472 is about 433.8193589446.

The spelling of 81644472 in words is "eighty-one million, six hundred forty-four thousand, four hundred seventy-two".