71661609 has 6 divisors (see below), whose sum is σ = 103511226. Its totient is φ = 47774400.

The previous prime is 71661599. The next prime is 71661661. The reversal of 71661609 is 90616617.

It can be written as a sum of positive squares in only one way, i.e., 66585600 + 5076009 = 8160^2 + 2253^2 .

It is not a de Polignac number, because 71661609 - 2⁴ = 71661593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (71661679) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3981192 + ... + 3981209.

It is an arithmetic number, because the mean of its divisors is an integer number (17251871).

Almost surely, 2^71661609 is an apocalyptic number.

It is an amenable number.

71661609 is a deficient number, since it is larger than the sum of its proper divisors (31849617).

71661609 is a wasteful number, since it uses less digits than its factorization.

71661609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7962407 (or 7962404 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 36.

The square root of 71661609 is about 8465.3180093839. The cubic root of 71661609 is about 415.3639986365.

The spelling of 71661609 in words is "seventy-one million, six hundred sixty-one thousand, six hundred nine".