71665509 has 4 divisors (see below), whose sum is σ = 95554016. Its totient is φ = 47777004.

The previous prime is 71665507. The next prime is 71665537. The reversal of 71665509 is 90556617.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90556617 = 3 ⋅30185539.

It is not a de Polignac number, because 71665509 - 2¹ = 71665507 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71665501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11944249 + ... + 11944254.

It is an arithmetic number, because the mean of its divisors is an integer number (23888504).

Almost surely, 2^71665509 is an apocalyptic number.

It is an amenable number.

71665509 is a deficient number, since it is larger than the sum of its proper divisors (23888507).

71665509 is a wasteful number, since it uses less digits than its factorization.

71665509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23888506.

The product of its (nonzero) digits is 56700, while the sum is 39.

The square root of 71665509 is about 8465.5483579033. The cubic root of 71665509 is about 415.3715335413.

The spelling of 71665509 in words is "seventy-one million, six hundred sixty-five thousand, five hundred nine".