81664208 has 10 divisors (see below), whose sum is σ = 158224434. Its totient is φ = 40832096.

The previous prime is 81664207. The next prime is 81664211. The reversal of 81664208 is 80246618.

It can be written as a sum of positive squares in only one way, i.e., 40857664 + 40806544 = 6392^2 + 6388^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81664207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2551991 + ... + 2552022.

Almost surely, 2^81664208 is an apocalyptic number.

It is an amenable number.

81664208 is a deficient number, since it is larger than the sum of its proper divisors (76560226).

81664208 is a wasteful number, since it uses less digits than its factorization.

81664208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5104021 (or 5104015 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 35.

The square root of 81664208 is about 9036.8251061974. The cubic root of 81664208 is about 433.8543119910.

The spelling of 81664208 in words is "eighty-one million, six hundred sixty-four thousand, two hundred eight".