21001021001 has 8 divisors (see below), whose sum is σ = 21212104008. Its totient is φ = 20790000000.

The previous prime is 21001020983. The next prime is 21001021003. The reversal of 21001021001 is 10012010012.

It can be written as a sum of positive squares in 4 ways, for example, as 11362494025 + 9638526976 = 106595^2 + 98176^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21001021001 - 2²⁶ = 20933912137 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21001021001.

It is not an unprimeable number, because it can be changed into a prime (21001021003) 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, 989501 + ... + 1010501.

It is an arithmetic number, because the mean of its divisors is an integer number (2651513001).

Almost surely, 2^21001021001 is an apocalyptic number.

It is an amenable number.

21001021001 is a deficient number, since it is larger than the sum of its proper divisors (211083007).

21001021001 is a wasteful number, since it uses less digits than its factorization.

21001021001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31003.

The product of its (nonzero) digits is 4, while the sum is 8.

Adding to 21001021001 its reverse (10012010012), we get a palindrome (31013031013).

The spelling of 21001021001 in words is "twenty-one billion, one million, twenty-one thousand, one".