21421121172 has 144 divisors (see below), whose sum is σ = 56099796480. Its totient is φ = 6307750400.

The previous prime is 21421121171. The next prime is 21421121203. The reversal of 21421121172 is 27112112412.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21421121171) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 119670979 + ... + 119671157.

It is an arithmetic number, because the mean of its divisors is an integer number (389581920).

Almost surely, 2^21421121172 is an apocalyptic number.

21421121172 is a gapful number since it is divisible by the number (22) 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 21421121172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28049898240).

21421121172 is an abundant number, since it is smaller than the sum of its proper divisors (34678675308).

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

21421121172 is a wasteful number, since it uses less digits than its factorization.

21421121172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 494 (or 379 counting only the distinct ones).

The product of its digits is 448, while the sum is 24.

Adding to 21421121172 its reverse (27112112412), we get a palindrome (48533233584).

The spelling of 21421121172 in words is "twenty-one billion, four hundred twenty-one million, one hundred twenty-one thousand, one hundred seventy-two".