21000000120 has 96 divisors (see below), whose sum is σ = 69247982160. Its totient is φ = 5090905600.

The previous prime is 21000000113. The next prime is 21000000121. The reversal of 21000000120 is 2100000012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a junction number, because it is equal to n+sod(n) for n = 21000000099 and 21000000108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000000121) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 708621 + ... + 737660.

Almost surely, 2^21000000120 is an apocalyptic number.

21000000120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000000120 is an abundant number, since it is smaller than the sum of its proper divisors (48247982040).

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

21000000120 is a wasteful number, since it uses less digits than its factorization.

21000000120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1446317 (or 1446302 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

Adding to 21000000120 its reverse (2100000012), we get a palindrome (23100000132).

The spelling of 21000000120 in words is "twenty-one billion, one hundred twenty", and thus it is an aban number.