21321001020 has 144 divisors (see below), whose sum is σ = 66271320864. Its totient is φ = 5117376000.

The previous prime is 21321001003. The next prime is 21321001021. The reversal of 21321001020 is 2010012312.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21321000987 and 21321001005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321001021) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 718722 + ... + 747798.

It is an arithmetic number, because the mean of its divisors is an integer number (460217506).

Almost surely, 2^21321001020 is an apocalyptic number.

21321001020 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 21321001020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33135660432).

21321001020 is an abundant number, since it is smaller than the sum of its proper divisors (44950319844).

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

21321001020 is a wasteful number, since it uses less digits than its factorization.

21321001020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29212 (or 29199 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

Adding to 21321001020 its reverse (2010012312), we get a palindrome (23331013332).

The spelling of 21321001020 in words is "twenty-one billion, three hundred twenty-one million, one thousand, twenty".