81664849 has 4 divisors (see below), whose sum is σ = 93331264. Its totient is φ = 69998436.

The previous prime is 81664813. The next prime is 81664859. The reversal of 81664849 is 94846618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81664849 - 2¹³ = 81656657 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81664799 and 81664808.

It is not an unprimeable number, because it can be changed into a prime (81664859) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5833197 + ... + 5833210.

It is an arithmetic number, because the mean of its divisors is an integer number (23332816).

Almost surely, 2^81664849 is an apocalyptic number.

It is an amenable number.

81664849 is a deficient number, since it is larger than the sum of its proper divisors (11666415).

81664849 is a wasteful number, since it uses less digits than its factorization.

81664849 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11666414.

The product of its digits is 331776, while the sum is 46.

The square root of 81664849 is about 9036.8605721235. The cubic root of 81664849 is about 433.8554471268.

The spelling of 81664849 in words is "eighty-one million, six hundred sixty-four thousand, eight hundred forty-nine".