21221216020 has 24 divisors (see below), whose sum is σ = 44569862568. Its totient is φ = 8487475200.

The previous prime is 21221216011. The next prime is 21221216021. The reversal of 21221216020 is 2061212212.

It can be written as a sum of positive squares in 4 ways, for example, as 6613592976 + 14607623044 = 81324^2 + 120862^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221216021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 122140 + ... + 239500.

It is an arithmetic number, because the mean of its divisors is an integer number (1857077607).

Almost surely, 2^21221216020 is an apocalyptic number.

21221216020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221216020 is an abundant number, since it is smaller than the sum of its proper divisors (23348646548).

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

21221216020 is a wasteful number, since it uses less digits than its factorization.

21221216020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126411 (or 126409 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

Adding to 21221216020 its reverse (2061212212), we get a palindrome (23282428232).

The spelling of 21221216020 in words is "twenty-one billion, two hundred twenty-one million, two hundred sixteen thousand, twenty".