71021665021 has 4 divisors (see below), whose sum is σ = 71044961500. Its totient is φ = 70998368544.

The previous prime is 71021665007. The next prime is 71021665073. The reversal of 71021665021 is 12056612017.

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 37021992921 + 33999672100 = 192411^2 + 184390^2 .

It is a cyclic number.

It is not a de Polignac number, because 71021665021 - 2⁹ = 71021664509 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 (71021665321) 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, 11643666 + ... + 11649763.

It is an arithmetic number, because the mean of its divisors is an integer number (17761240375).

Almost surely, 2^71021665021 is an apocalyptic number.

It is an amenable number.

71021665021 is a deficient number, since it is larger than the sum of its proper divisors (23296479).

71021665021 is a wasteful number, since it uses less digits than its factorization.

71021665021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23296478.

The product of its (nonzero) digits is 5040, while the sum is 31.

The spelling of 71021665021 in words is "seventy-one billion, twenty-one million, six hundred sixty-five thousand, twenty-one".