81605842 has 4 divisors (see below), whose sum is σ = 122408766. Its totient is φ = 40802920.

The previous prime is 81605837. The next prime is 81605869. The reversal of 81605842 is 24850618.

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., 70576801 + 11029041 = 8401^2 + 3321^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81605798 and 81605807.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20401459 + ... + 20401462.

Almost surely, 2^81605842 is an apocalyptic number.

81605842 is a deficient number, since it is larger than the sum of its proper divisors (40802924).

81605842 is a wasteful number, since it uses less digits than its factorization.

81605842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40802923.

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

The square root of 81605842 is about 9033.5951868567. The cubic root of 81605842 is about 433.7509277526.

The spelling of 81605842 in words is "eighty-one million, six hundred five thousand, eight hundred forty-two".