21121100440 has 64 divisors (see below), whose sum is σ = 52034296320. Its totient is φ = 7652016000.

The previous prime is 21121100423. The next prime is 21121100443. The reversal of 21121100440 is 4400112112.

It is a happy number.

It is a super-2 number, since 2×21121100440² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121100443) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30675 + ... + 207805.

It is an arithmetic number, because the mean of its divisors is an integer number (813035880).

Almost surely, 2^21121100440 is an apocalyptic number.

21121100440 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 21121100440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26017148160).

21121100440 is an abundant number, since it is smaller than the sum of its proper divisors (30913195880).

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

21121100440 is a wasteful number, since it uses less digits than its factorization.

21121100440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177424 (or 177420 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21121100440 its reverse (4400112112), we get a palindrome (25521212552).

The spelling of 21121100440 in words is "twenty-one billion, one hundred twenty-one million, one hundred thousand, four hundred forty".