81644508 has 54 divisors (see below), whose sum is σ = 226858632. Its totient is φ = 24739440.

The previous prime is 81644491. The next prime is 81644509. The reversal of 81644508 is 80544618.

81644508 is a `hidden beast` number, since 8 + 1 + 644 + 5 + 0 + 8 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81644509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 5016 + ... + 13727.

Almost surely, 2^81644508 is an apocalyptic number.

It is an amenable number.

81644508 is an abundant number, since it is smaller than the sum of its proper divisors (145214124).

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

81644508 is a wasteful number, since it uses less digits than its factorization.

81644508 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18775 (or 18759 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The square root of 81644508 is about 9035.7350558767. The cubic root of 81644508 is about 433.8194227068.

The spelling of 81644508 in words is "eighty-one million, six hundred forty-four thousand, five hundred eight".