71721647 has 4 divisors (see below), whose sum is σ = 71955576. Its totient is φ = 71487720.

The previous prime is 71721563. The next prime is 71721649. The reversal of 71721647 is 74612717.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74612717 = 6791 ⋅10987.

It is a cyclic number.

It is not a de Polignac number, because 71721647 - 2¹⁸ = 71459503 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 (71721649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 116504 + ... + 117117.

It is an arithmetic number, because the mean of its divisors is an integer number (17988894).

Almost surely, 2^71721647 is an apocalyptic number.

71721647 is a deficient number, since it is larger than the sum of its proper divisors (233929).

71721647 is a wasteful number, since it uses less digits than its factorization.

71721647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 233928.

The product of its digits is 16464, while the sum is 35.

The square root of 71721647 is about 8468.8633830048. The cubic root of 71721647 is about 415.4799633913.

The spelling of 71721647 in words is "seventy-one million, seven hundred twenty-one thousand, six hundred forty-seven".