81566942 has 4 divisors (see below), whose sum is σ = 122350416. Its totient is φ = 40783470.

The previous prime is 81566941. The next prime is 81566951. The reversal of 81566942 is 24966518.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 24966518 = 2 ⋅12483259.

It is a self number, because there is not a number n which added to its sum of digits gives 81566942.

It is a congruent number.

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 as a sum of consecutive naturals, namely, 20391734 + ... + 20391737.

It is an arithmetic number, because the mean of its divisors is an integer number (30587604).

Almost surely, 2^81566942 is an apocalyptic number.

81566942 is a deficient number, since it is larger than the sum of its proper divisors (40783474).

81566942 is a wasteful number, since it uses less digits than its factorization.

81566942 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40783473.

The product of its digits is 103680, while the sum is 41.

The square root of 81566942 is about 9031.4418560936. The cubic root of 81566942 is about 433.6819964425.

The spelling of 81566942 in words is "eighty-one million, five hundred sixty-six thousand, nine hundred forty-two".