2100120021 has 16 divisors (see below), whose sum is σ = 3112070400. Its totient is φ = 1399728384.

The previous prime is 2100120019. The next prime is 2100120047. The reversal of 2100120021 is 1200210012.

It is not a de Polignac number, because 2100120021 - 2¹ = 2100120019 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 2100119985 and 2100120012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2100120221) 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, 143380 + ... + 157346.

It is an arithmetic number, because the mean of its divisors is an integer number (194504400).

Almost surely, 2^2100120021 is an apocalyptic number.

It is an amenable number.

2100120021 is a deficient number, since it is larger than the sum of its proper divisors (1011950379).

2100120021 is a wasteful number, since it uses less digits than its factorization.

2100120021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19545 (or 19539 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 2100120021 is about 45827.0664673182. The cubic root of 2100120021 is about 1280.6035607754.

Adding to 2100120021 its reverse (1200210012), we get a palindrome (3300330033).

The spelling of 2100120021 in words is "two billion, one hundred million, one hundred twenty thousand, twenty-one".