71511720671021 has 24 divisors (see below), whose sum is σ = 78182650649880. Its totient is φ = 65322564338304.

The previous prime is 71511720671003. The next prime is 71511720671023. The reversal of 71511720671021 is 12017602711517.

It can be written as a sum of positive squares in 4 ways, for example, as 28076634990121 + 43435085680900 = 5298739^2 + 6590530^2 .

It is not a de Polignac number, because 71511720671021 - 2³⁸ = 71236842764077 is a prime.

It is a super-2 number, since 2×71511720671021² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 71511720671021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71511720671023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3014291 + ... + 12333263.

It is an arithmetic number, because the mean of its divisors is an integer number (3257610443745).

Almost surely, 2^{71511720671021} is an apocalyptic number.

It is an amenable number.

71511720671021 is a deficient number, since it is larger than the sum of its proper divisors (6670929978859).

71511720671021 is a wasteful number, since it uses less digits than its factorization.

71511720671021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9319773 (or 9319754 counting only the distinct ones).

The product of its (nonzero) digits is 41160, while the sum is 41.

The spelling of 71511720671021 in words is "seventy-one trillion, five hundred eleven billion, seven hundred twenty million, six hundred seventy-one thousand, twenty-one".