21002121021 has 16 divisors (see below), whose sum is σ = 32012734464. Its totient is φ = 11997648624.

The previous prime is 21002121013. The next prime is 21002121043. The reversal of 21002121021 is 12012120012.

It is not a de Polignac number, because 21002121021 - 2³ = 21002121013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21002120988 and 21002121006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002121061) 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, 75225 + ... + 218318.

It is an arithmetic number, because the mean of its divisors is an integer number (2000795904).

Almost surely, 2^21002121021 is an apocalyptic number.

21002121021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21002121021 is a deficient number, since it is larger than the sum of its proper divisors (11010613443).

21002121021 is a wasteful number, since it uses less digits than its factorization.

21002121021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296960.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21002121021 its reverse (12012120012), we get a palindrome (33014241033).

The spelling of 21002121021 in words is "twenty-one billion, two million, one hundred twenty-one thousand, twenty-one".