81566641 has 8 divisors (see below), whose sum is σ = 88369344. Its totient is φ = 74839440.

The previous prime is 81566633. The next prime is 81566659. The reversal of 81566641 is 14666518.

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

It is not a de Polignac number, because 81566641 - 2³ = 81566633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81566641.

It is not an unprimeable number, because it can be changed into a prime (81566941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16615 + ... + 20956.

It is an arithmetic number, because the mean of its divisors is an integer number (11046168).

Almost surely, 2^81566641 is an apocalyptic number.

It is an amenable number.

81566641 is a deficient number, since it is larger than the sum of its proper divisors (6802703).

81566641 is a wasteful number, since it uses less digits than its factorization.

81566641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37751.

The product of its digits is 34560, while the sum is 37.

The square root of 81566641 is about 9031.4251920724. The cubic root of 81566641 is about 433.6814629811.

The spelling of 81566641 in words is "eighty-one million, five hundred sixty-six thousand, six hundred forty-one".