21001001001001 has 4 divisors (see below), whose sum is σ = 24001144001152. Its totient is φ = 18000858000852.

The previous prime is 21001001000999. The next prime is 21001001001061. The reversal of 21001001001001 is 10010010010012.

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 21001001001001 - 2¹ = 21001001000999 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (7), and also a Moran number because the ratio is a prime number: 3000143000143 = 21001001001001 / (2 + 1 + 0 + 0 + 1 + 0 + 0 + 1 + 0 + 0 + 1 + 0 + 0 + 1).

It is a Duffinian number.

21001001001001 is a modest number, since divided by 1001001 gives 21001 as remainder.

It is not an unprimeable number, because it can be changed into a prime (21001001001061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1500071500065 + ... + 1500071500078.

It is an arithmetic number, because the mean of its divisors is an integer number (6000286000288).

Almost surely, 2^{21001001001001} is an apocalyptic number.

It is an amenable number.

21001001001001 is a deficient number, since it is larger than the sum of its proper divisors (3000143000151).

21001001001001 is an equidigital number, since it uses as much as digits as its factorization.

21001001001001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3000143000150.

The product of its (nonzero) digits is 2, while the sum is 7.

Adding to 21001001001001 its reverse (10010010010012), we get a palindrome (31011011011013).

It can be divided in two parts, 2 and 1001001001001, that multiplied together give a palindrome (2002002002002).

The spelling of 21001001001001 in words is "twenty-one trillion, one billion, one million, one thousand, one".