81644256 has 36 divisors (see below), whose sum is σ = 232176672. Its totient is φ = 27214656.

The previous prime is 81644219. The next prime is 81644261. The reversal of 81644256 is 65244618.

81644256 is a `hidden beast` number, since 8 + 1 + 644 + 2 + 5 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-3 number, since 3×81644256³ (a number of 25 digits) contains 333 as substring.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81644256.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 141456 + ... + 142031.

It is an arithmetic number, because the mean of its divisors is an integer number (6449352).

Almost surely, 2^81644256 is an apocalyptic number.

It is an amenable number.

81644256 is an abundant number, since it is smaller than the sum of its proper divisors (150532416).

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

81644256 is a wasteful number, since it uses less digits than its factorization.

81644256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 283503 (or 283492 counting only the distinct ones).

The product of its digits is 46080, while the sum is 36.

The square root of 81644256 is about 9035.7211112340. The cubic root of 81644256 is about 433.8189763709.

The spelling of 81644256 in words is "eighty-one million, six hundred forty-four thousand, two hundred fifty-six".