21200120021 has 8 divisors (see below), whose sum is σ = 21700731360. Its totient is φ = 20699853552.

The previous prime is 21200119961. The next prime is 21200120087. The reversal of 21200120021 is 12002100212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21200120021 - 2⁶ = 21200119957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21200119984 and 21200120011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21200120321) 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 7 ways as a sum of consecutive naturals, for example, 40346 + ... + 209828.

It is an arithmetic number, because the mean of its divisors is an integer number (2712591420).

Almost surely, 2^21200120021 is an apocalyptic number.

It is an amenable number.

21200120021 is a deficient number, since it is larger than the sum of its proper divisors (500611339).

21200120021 is a wasteful number, since it uses less digits than its factorization.

21200120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172435.

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

Adding to 21200120021 its reverse (12002100212), we get a palindrome (33202220233).

The spelling of 21200120021 in words is "twenty-one billion, two hundred million, one hundred twenty thousand, twenty-one".