71730781 has 4 divisors (see below), whose sum is σ = 71783100. Its totient is φ = 71678464.

The previous prime is 71730779. The next prime is 71730793. The reversal of 71730781 is 18703717.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7650756 + 64080025 = 2766^2 + 8005^2 .

It is a cyclic number.

It is not a de Polignac number, because 71730781 - 2¹ = 71730779 is a prime.

It is a super-2 number, since 2×71730781² = 10290609885739922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71730731) 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, 24046 + ... + 26863.

It is an arithmetic number, because the mean of its divisors is an integer number (17945775).

Almost surely, 2^71730781 is an apocalyptic number.

It is an amenable number.

71730781 is a deficient number, since it is larger than the sum of its proper divisors (52319).

71730781 is a wasteful number, since it uses less digits than its factorization.

71730781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52318.

The product of its (nonzero) digits is 8232, while the sum is 34.

The square root of 71730781 is about 8469.4026353693. The cubic root of 71730781 is about 415.4976002464.

The spelling of 71730781 in words is "seventy-one million, seven hundred thirty thousand, seven hundred eighty-one".