2001721291684 has 27 divisors (see below), whose sum is σ = 3662058156897. Its totient is φ = 957313839504.

The previous prime is 2001721291681. The next prime is 2001721291693. The reversal of 2001721291684 is 4861921271002.

The square root of 2001721291684 is 1414822.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 829975660900 + 1171745630784 = 911030^2 + 1082472^2 .

It is a super-2 number, since 2×2001721291684² (a number of 25 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 2001721291684.

It is not an unprimeable number, because it can be changed into a prime (2001721291681) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 65066434 + ... + 65097190.

Almost surely, 2^{2001721291684} is an apocalyptic number.

2001721291684 is the 1414822-nd square number.

It is an amenable number.

2001721291684 is a deficient number, since it is larger than the sum of its proper divisors (1660336865213).

2001721291684 is an frugal number, since it uses more digits than its factorization.

2001721291684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61564 (or 30782 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 43.

The spelling of 2001721291684 in words is "two trillion, one billion, seven hundred twenty-one million, two hundred ninety-one thousand, six hundred eighty-four".