2001997721 has 8 divisors (see below), whose sum is σ = 2060501184. Its totient is φ = 1944336240.

The previous prime is 2001997691. The next prime is 2001997727. The reversal of 2001997721 is 1277991002.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2001997721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2001997727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 205670 + ... + 215183.

It is an arithmetic number, because the mean of its divisors is an integer number (257562648).

Almost surely, 2^2001997721 is an apocalyptic number.

It is an amenable number.

2001997721 is a deficient number, since it is larger than the sum of its proper divisors (58503463).

2001997721 is an equidigital number, since it uses as much as digits as its factorization.

2001997721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420991.

The product of its (nonzero) digits is 15876, while the sum is 38.

The square root of 2001997721 is about 44743.6891751228. The cubic root of 2001997721 is about 1260.3404054232.

The spelling of 2001997721 in words is "two billion, one million, nine hundred ninety-seven thousand, seven hundred twenty-one".