81266661 has 24 divisors (see below), whose sum is σ = 134484480. Its totient is φ = 46323936.

The previous prime is 81266657. The next prime is 81266677. The reversal of 81266661 is 16666218.

It is not a de Polignac number, because 81266661 - 2² = 81266657 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81266611) 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 23 ways as a sum of consecutive naturals, for example, 28831 + ... + 31523.

It is an arithmetic number, because the mean of its divisors is an integer number (5603520).

Almost surely, 2^81266661 is an apocalyptic number.

It is an amenable number.

81266661 is a deficient number, since it is larger than the sum of its proper divisors (53217819).

81266661 is a wasteful number, since it uses less digits than its factorization.

81266661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3185 (or 3182 counting only the distinct ones).

The product of its digits is 20736, while the sum is 36.

The square root of 81266661 is about 9014.8023272837. The cubic root of 81266661 is about 433.1491555901.

The spelling of 81266661 in words is "eighty-one million, two hundred sixty-six thousand, six hundred sixty-one".