21210120020 has 24 divisors (see below), whose sum is σ = 45978067968. Its totient is φ = 8210368800.

The previous prime is 21210120017. The next prime is 21210120037. The reversal of 21210120020 is 2002101212.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21210119983 and 21210120010.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17104316 + ... + 17105555.

It is an arithmetic number, because the mean of its divisors is an integer number (1915752832).

Almost surely, 2^21210120020 is an apocalyptic number.

21210120020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21210120020 is an abundant number, since it is smaller than the sum of its proper divisors (24767947948).

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

21210120020 is a wasteful number, since it uses less digits than its factorization.

21210120020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34209911 (or 34209909 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21210120020 its reverse (2002101212), we get a palindrome (23212221232).

The spelling of 21210120020 in words is "twenty-one billion, two hundred ten million, one hundred twenty thousand, twenty".