21001211020 has 48 divisors (see below), whose sum is σ = 45544117248. Its totient is φ = 8126124480.

The previous prime is 21001210991. The next prime is 21001211027. The reversal of 21001211020 is 2011210012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21001210988 and 21001211006.

It is not an unprimeable number, because it can be changed into a prime (21001211027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1905967 + ... + 1916953.

It is an arithmetic number, because the mean of its divisors is an integer number (948835776).

Almost surely, 2^21001211020 is an apocalyptic number.

21001211020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001211020 is an abundant number, since it is smaller than the sum of its proper divisors (24542906228).

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

21001211020 is a wasteful number, since it uses less digits than its factorization.

21001211020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14110 (or 14108 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21001211020 its reverse (2011210012), we get a palindrome (23012421032).

The spelling of 21001211020 in words is "twenty-one billion, one million, two hundred eleven thousand, twenty".