2001221101981 has 4 divisors (see below), whose sum is σ = 2001268246432. Its totient is φ = 2001173957532.

The previous prime is 2001221101949. The next prime is 2001221101987. The reversal of 2001221101981 is 1891011221002.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2001221101981 - 2⁵ = 2001221101949 is a prime.

It is a super-2 number, since 2×2001221101981² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2001221101987) 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, 23508495 + ... + 23593468.

It is an arithmetic number, because the mean of its divisors is an integer number (500317061608).

Almost surely, 2^{2001221101981} is an apocalyptic number.

It is an amenable number.

2001221101981 is a deficient number, since it is larger than the sum of its proper divisors (47144451).

2001221101981 is an equidigital number, since it uses as much as digits as its factorization.

2001221101981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47144450.

The product of its (nonzero) digits is 576, while the sum is 28.

Adding to 2001221101981 its reverse (1891011221002), we get a palindrome (3892232322983).

The spelling of 2001221101981 in words is "two trillion, one billion, two hundred twenty-one million, one hundred one thousand, nine hundred eighty-one".