81665742 has 16 divisors (see below), whose sum is σ = 164012112. Its totient is φ = 27108480.

The previous prime is 81665741. The next prime is 81665761. The reversal of 81665742 is 24756618.

It is a self number, because there is not a number n which added to its sum of digits gives 81665742.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81665741) 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, 26793 + ... + 29684.

It is an arithmetic number, because the mean of its divisors is an integer number (10250757).

Almost surely, 2^81665742 is an apocalyptic number.

81665742 is an abundant number, since it is smaller than the sum of its proper divisors (82346370).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81665742 is a wasteful number, since it uses less digits than its factorization.

81665742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56723.

The product of its digits is 80640, while the sum is 39.

The square root of 81665742 is about 9036.9099807401. The cubic root of 81665742 is about 433.8570285150.

The spelling of 81665742 in words is "eighty-one million, six hundred sixty-five thousand, seven hundred forty-two".