81666613 has 8 divisors (see below), whose sum is σ = 93401280. Its totient is φ = 69948960.

The previous prime is 81666601. The next prime is 81666619. The reversal of 81666613 is 31666618.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81666613 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81666619) by changing a digit.

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, 8658 + ... + 15436.

It is an arithmetic number, because the mean of its divisors is an integer number (11675160).

Almost surely, 2^81666613 is an apocalyptic number.

It is an amenable number.

81666613 is a deficient number, since it is larger than the sum of its proper divisors (11734667).

81666613 is a wasteful number, since it uses less digits than its factorization.

81666613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8507.

The product of its digits is 31104, while the sum is 37.

The square root of 81666613 is about 9036.9581718629. The cubic root of 81666613 is about 433.8585709330.

The spelling of 81666613 in words is "eighty-one million, six hundred sixty-six thousand, six hundred thirteen".