21001001020 has 12 divisors (see below), whose sum is σ = 44102102184. Its totient is φ = 8400400400.

The previous prime is 21001001009. The next prime is 21001001041. The reversal of 21001001020 is 2010010012.

It is a junction number, because it is equal to n+sod(n) for n = 21001000994 and 21001001012.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 525025006 + ... + 525025045.

It is an arithmetic number, because the mean of its divisors is an integer number (3675175182).

Almost surely, 2^21001001020 is an apocalyptic number.

21001001020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001001020 is an abundant number, since it is smaller than the sum of its proper divisors (23101101164).

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

21001001020 is a wasteful number, since it uses less digits than its factorization.

21001001020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1050050060 (or 1050050058 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21001001020 its reverse (2010010012), we get a palindrome (23011011032).

The spelling of 21001001020 in words is "twenty-one billion, one million, one thousand, twenty".