21021255220 has 48 divisors (see below), whose sum is σ = 50732922240. Its totient is φ = 7167014784.

The previous prime is 21021255209. The next prime is 21021255239. The reversal of 21021255220 is 2255212012.

It is a junction number, because it is equal to n+sod(n) for n = 21021255191 and 21021255200.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 394359 + ... + 444478.

It is an arithmetic number, because the mean of its divisors is an integer number (1056935880).

Almost surely, 2^21021255220 is an apocalyptic number.

21021255220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021255220 is an abundant number, since it is smaller than the sum of its proper divisors (29711667020).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21021255220 is a wasteful number, since it uses less digits than its factorization.

21021255220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 839032 (or 839030 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 22.

Adding to 21021255220 its reverse (2255212012), we get a palindrome (23276467232).

The spelling of 21021255220 in words is "twenty-one billion, twenty-one million, two hundred fifty-five thousand, two hundred twenty".