21020200120 has 64 divisors (see below), whose sum is σ = 50157921600. Its totient is φ = 7900784640.

The previous prime is 21020200081. The next prime is 21020200127. The reversal of 21020200120 is 2100202012.

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 = 21020200097 and 21020200106.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020200127) 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, 404586 + ... + 453574.

It is an arithmetic number, because the mean of its divisors is an integer number (783717525).

Almost surely, 2^21020200120 is an apocalyptic number.

21020200120 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 21020200120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25078960800).

21020200120 is an abundant number, since it is smaller than the sum of its proper divisors (29137721480).

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

21020200120 is a wasteful number, since it uses less digits than its factorization.

21020200120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49648 (or 49644 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21020200120 its reverse (2100202012), we get a palindrome (23120402132).

The spelling of 21020200120 in words is "twenty-one billion, twenty million, two hundred thousand, one hundred twenty".