21010020121 has 4 divisors (see below), whose sum is σ = 21010806544. Its totient is φ = 21009233700.

The previous prime is 21010020113. The next prime is 21010020131. The reversal of 21010020121 is 12102001012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21010020121 - 2³ = 21010020113 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21010020098 and 21010020107.

It is not an unprimeable number, because it can be changed into a prime (21010020131) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 351675 + ... + 407056.

It is an arithmetic number, because the mean of its divisors is an integer number (5252701636).

Almost surely, 2^21010020121 is an apocalyptic number.

It is an amenable number.

21010020121 is a deficient number, since it is larger than the sum of its proper divisors (786423).

21010020121 is an equidigital number, since it uses as much as digits as its factorization.

21010020121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 786422.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21010020121 its reverse (12102001012), we get a palindrome (33112021133).

The spelling of 21010020121 in words is "twenty-one billion, ten million, twenty thousand, one hundred twenty-one".