81788066 has 4 divisors (see below), whose sum is σ = 122682102. Its totient is φ = 40894032.

The previous prime is 81788011. The next prime is 81788087. The reversal of 81788066 is 66088718.

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., 81522841 + 265225 = 9029^2 + 515^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20447015 + ... + 20447018.

Almost surely, 2^81788066 is an apocalyptic number.

81788066 is a deficient number, since it is larger than the sum of its proper divisors (40894036).

81788066 is a wasteful number, since it uses less digits than its factorization.

81788066 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40894035.

The product of its (nonzero) digits is 129024, while the sum is 44.

The square root of 81788066 is about 9043.6754696307. The cubic root of 81788066 is about 434.0735397479.

The spelling of 81788066 in words is "eighty-one million, seven hundred eighty-eight thousand, sixty-six".