21221021221020 has 144 divisors (see below), whose sum is σ = 65470833792000. Its totient is φ = 5562227776896.

The previous prime is 21221021220967. The next prime is 21221021221033. The reversal of 21221021221020 is 2012212012212.

It is a happy number.

21221021221020 is a `hidden beast` number, since 2 + 1 + 221 + 0 + 212 + 210 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21221021220984 and 21221021221002.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 75889021 + ... + 76168139.

It is an arithmetic number, because the mean of its divisors is an integer number (454658568000).

Almost surely, 2^{21221021221020} is an apocalyptic number.

21221021221020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21221021221020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32735416896000).

21221021221020 is an abundant number, since it is smaller than the sum of its proper divisors (44249812570980).

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

21221021221020 is a wasteful number, since it uses less digits than its factorization.

21221021221020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286352 (or 286347 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 21221021221020 its reverse (2012212012212), we get a palindrome (23233233233232).

The spelling of 21221021221020 in words is "twenty-one trillion, two hundred twenty-one billion, twenty-one million, two hundred twenty-one thousand, twenty".