21221121024 has 132 divisors (see below), whose sum is σ = 62116886416. Its totient is φ = 6976585728.

The previous prime is 21221121013. The next prime is 21221121041. The reversal of 21221121024 is 42012112212.

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 = 21221120988 and 21221121006.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 656997 + ... + 688539.

Almost surely, 2^21221121024 is an apocalyptic number.

21221121024 is a gapful number since it is divisible by the number (24) 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 21221121024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31058443208).

21221121024 is an abundant number, since it is smaller than the sum of its proper divisors (40895765392).

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

21221121024 is a wasteful number, since it uses less digits than its factorization.

21221121024 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31642 (or 31621 counting only the distinct ones).

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

Adding to 21221121024 its reverse (42012112212), we get a palindrome (63233233236).

The spelling of 21221121024 in words is "twenty-one billion, two hundred twenty-one million, one hundred twenty-one thousand, twenty-four".