21001001001 has 8 divisors (see below), whose sum is σ = 28010677344. Its totient is φ = 13995996000.

The previous prime is 21001000991. The next prime is 21001001009. The reversal of 21001001001 is 10010010012.

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

It is a de Polignac number, because none of the positive numbers 2^k-21001001001 is a prime.

21001001001 is a modest number, since divided by 1001001 gives 21 as remainder.

It is not an unprimeable number, because it can be changed into a prime (21001001009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1157331 + ... + 1175336.

It is an arithmetic number, because the mean of its divisors is an integer number (3501334668).

Almost surely, 2^21001001001 is an apocalyptic number.

It is an amenable number.

21001001001 is a deficient number, since it is larger than the sum of its proper divisors (7009676343).

21001001001 is a wasteful number, since it uses less digits than its factorization.

21001001001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2335671.

The product of its (nonzero) digits is 2, while the sum is 6.

Adding to 21001001001 its reverse (10010010012), we get a palindrome (31011011013).

It can be divided in two parts, 2 and 1001001001, that multiplied together give a palindrome (2002002002).

The spelling of 21001001001 in words is "twenty-one billion, one million, one thousand, one".