21021001001 has 24 divisors (see below), whose sum is σ = 28437834432. Its totient is φ = 15119992800.

The previous prime is 21021000989. The next prime is 21021001003. The reversal of 21021001001 is 10010012012.

It is not a de Polignac number, because 21021001001 - 2¹⁴ = 21020984617 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21021001001.

It is not an unprimeable number, because it can be changed into a prime (21021001003) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 943535 + ... + 965556.

It is an arithmetic number, because the mean of its divisors is an integer number (1184909768).

Almost surely, 2^21021001001 is an apocalyptic number.

It is an amenable number.

21021001001 is a deficient number, since it is larger than the sum of its proper divisors (7416833431).

21021001001 is a wasteful number, since it uses less digits than its factorization.

21021001001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1909133 (or 1909122 counting only the distinct ones).

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

Adding to 21021001001 its reverse (10010012012), we get a palindrome (31031013013).

The spelling of 21021001001 in words is "twenty-one billion, twenty-one million, one thousand, one".