21002020121 has 8 divisors (see below), whose sum is σ = 21259751520. Its totient is φ = 20744400672.

The previous prime is 21002020103. The next prime is 21002020163. The reversal of 21002020121 is 12102020012.

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 21002020121 - 2²² = 20997825817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002020181) 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, 386966 + ... + 437888.

It is an arithmetic number, because the mean of its divisors is an integer number (2657468940).

Almost surely, 2^21002020121 is an apocalyptic number.

It is an amenable number.

21002020121 is a deficient number, since it is larger than the sum of its proper divisors (257731399).

21002020121 is an equidigital number, since it uses as much as digits as its factorization.

21002020121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55975.

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

Adding to 21002020121 its reverse (12102020012), we get a palindrome (33104040133).

The spelling of 21002020121 in words is "twenty-one billion, two million, twenty thousand, one hundred twenty-one".