21001001001000 has 128 divisors (see below), whose sum is σ = 65544984984960. Its totient is φ = 5598398400000.

The previous prime is 21001001000999. The next prime is 21001001001061. The reversal of 21001001001000 is 10010010012.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21001001001000.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7836667 + ... + 10169333.

It is an arithmetic number, because the mean of its divisors is an integer number (512070195195).

Almost surely, 2^{21001001001000} is an apocalyptic number.

21001001001000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21001001001000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32772492492480).

21001001001000 is an abundant number, since it is smaller than the sum of its proper divisors (44543983983960).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21001001001000 is a wasteful number, since it uses less digits than its factorization.

21001001001000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2335692 (or 2335678 counting only the distinct ones).

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

Adding to 21001001001000 its reverse (10010010012), we get a palindrome (21011011011012).

The spelling of 21001001001000 in words is "twenty-one trillion, one billion, one million, one thousand".