81004644 has 72 divisors (see below), whose sum is σ = 244315680. Its totient is φ = 23142672.

The previous prime is 81004633. The next prime is 81004661. The reversal of 81004644 is 44640018.

81004644 is a `hidden beast` number, since 8 + 10 + 0 + 4 + 644 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2362 + ... + 12945.

Almost surely, 2^81004644 is an apocalyptic number.

81004644 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81004644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122157840).

81004644 is an abundant number, since it is smaller than the sum of its proper divisors (163311036).

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

81004644 is a wasteful number, since it uses less digits than its factorization.

81004644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15334 (or 15319 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 81004644 is about 9000.2579963021. The cubic root of 81004644 is about 432.6831398317.

The spelling of 81004644 in words is "eighty-one million, four thousand, six hundred forty-four".