21000220021 has 16 divisors (see below), whose sum is σ = 23157794880. Its totient is φ = 18884638080.

The previous prime is 21000220019. The next prime is 21000220039. The reversal of 21000220021 is 12002200012.

It is not a de Polignac number, because 21000220021 - 2¹ = 21000220019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000220121) 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, 725590 + ... + 753976.

It is an arithmetic number, because the mean of its divisors is an integer number (1447362180).

Almost surely, 2^21000220021 is an apocalyptic number.

It is an amenable number.

21000220021 is a deficient number, since it is larger than the sum of its proper divisors (2157574859).

21000220021 is a wasteful number, since it uses less digits than its factorization.

21000220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29124.

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21000220021 its reverse (12002200012), we get a palindrome (33002420033).

The spelling of 21000220021 in words is "twenty-one billion, two hundred twenty thousand, twenty-one".