21242122400 has 72 divisors (see below), whose sum is σ = 51890428800. Its totient is φ = 8491426560.

The previous prime is 21242122381. The next prime is 21242122409. The reversal of 21242122400 is 422124212.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (21242122409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1390001 + ... + 1405199.

It is an arithmetic number, because the mean of its divisors is an integer number (720700400).

Almost surely, 2^21242122400 is an apocalyptic number.

21242122400 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 21242122400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25945214400).

21242122400 is an abundant number, since it is smaller than the sum of its proper divisors (30648306400).

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

21242122400 is a wasteful number, since it uses less digits than its factorization.

21242122400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16966 (or 16953 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 20.

Adding to 21242122400 its reverse (422124212), we get a palindrome (21664246612).

The spelling of 21242122400 in words is "twenty-one billion, two hundred forty-two million, one hundred twenty-two thousand, four hundred".