2021171660721 has 24 divisors (see below), whose sum is σ = 3046649126976. Its totient is φ = 1288759237920.

The previous prime is 2021171660707. The next prime is 2021171660723. The reversal of 2021171660721 is 1270661711202.

2021171660721 is a `hidden beast` number, since 2 + 0 + 2 + 1 + 17 + 16 + 607 + 21 = 666.

It is not a de Polignac number, because 2021171660721 - 2¹⁸ = 2021171398577 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2021171660723) 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, 2223826 + ... + 2997956.

It is an arithmetic number, because the mean of its divisors is an integer number (126943713624).

Almost surely, 2^{2021171660721} is an apocalyptic number.

It is an amenable number.

2021171660721 is a deficient number, since it is larger than the sum of its proper divisors (1025477466255).

2021171660721 is a wasteful number, since it uses less digits than its factorization.

2021171660721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 786773 (or 786770 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The spelling of 2021171660721 in words is "two trillion, twenty-one billion, one hundred seventy-one million, six hundred sixty thousand, seven hundred twenty-one".