81647664 has 40 divisors (see below), whose sum is σ = 241056000. Its totient is φ = 23327808.

The previous prime is 81647639. The next prime is 81647711. The reversal of 81647664 is 46674618.

It is a Harshad number since it is a multiple of its sum of digits (42).

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121164 + ... + 121835.

It is an arithmetic number, because the mean of its divisors is an integer number (6026400).

Almost surely, 2^81647664 is an apocalyptic number.

81647664 is a gapful number since it is divisible by the number (84) formed by its first and last digit.

It is an amenable number.

81647664 is an abundant number, since it is smaller than the sum of its proper divisors (159408336).

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

81647664 is a wasteful number, since it uses less digits than its factorization.

81647664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243017 (or 243011 counting only the distinct ones).

The product of its digits is 193536, while the sum is 42.

The square root of 81647664 is about 9035.9096941039. The cubic root of 81647664 is about 433.8250124539.

The spelling of 81647664 in words is "eighty-one million, six hundred forty-seven thousand, six hundred sixty-four".