71521317221 has 4 divisors (see below), whose sum is σ = 73184603712. Its totient is φ = 69858030732.

The previous prime is 71521317173. The next prime is 71521317223. The reversal of 71521317221 is 12271312517.

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: 12271312517 = 7639 ⋅1606403.

It is a cyclic number.

It is not a de Polignac number, because 71521317221 - 2³⁴ = 54341448037 is a prime.

It is a super-2 number, since 2×71521317221² (a number of 23 digits) 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 (71521317223) 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, 831643181 + ... + 831643266.

It is an arithmetic number, because the mean of its divisors is an integer number (18296150928).

Almost surely, 2^71521317221 is an apocalyptic number.

It is an amenable number.

71521317221 is a deficient number, since it is larger than the sum of its proper divisors (1663286491).

71521317221 is a wasteful number, since it uses less digits than its factorization.

71521317221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1663286490.

The product of its digits is 5880, while the sum is 32.

Adding to 71521317221 its reverse (12271312517), we get a palindrome (83792629738).

The spelling of 71521317221 in words is "seventy-one billion, five hundred twenty-one million, three hundred seventeen thousand, two hundred twenty-one".