81506842 has 4 divisors (see below), whose sum is σ = 122260266. Its totient is φ = 40753420.

The previous prime is 81506839. The next prime is 81506851. The reversal of 81506842 is 24860518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 77422401 + 4084441 = 8799^2 + 2021^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81506798 and 81506807.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20376709 + ... + 20376712.

Almost surely, 2^81506842 is an apocalyptic number.

81506842 is a deficient number, since it is larger than the sum of its proper divisors (40753424).

81506842 is a wasteful number, since it uses less digits than its factorization.

81506842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40753423.

The product of its (nonzero) digits is 15360, while the sum is 34.

The square root of 81506842 is about 9028.1139780133. The cubic root of 81506842 is about 433.5754553548.

The spelling of 81506842 in words is "eighty-one million, five hundred six thousand, eight hundred forty-two".