21212031440 has 40 divisors (see below), whose sum is σ = 51018598440. Its totient is φ = 8192231936.

The previous prime is 21212031431. The next prime is 21212031443. The reversal of 21212031440 is 4413021212.

It can be written as a sum of positive squares in 4 ways, for example, as 25482304 + 21186549136 = 5048^2 + 145556^2 .

It is a tau number, because it is divible by the number of its divisors (40).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212031443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4569239 + ... + 4573878.

It is an arithmetic number, because the mean of its divisors is an integer number (1275464961).

Almost surely, 2^21212031440 is an apocalyptic number.

21212031440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212031440 is an abundant number, since it is smaller than the sum of its proper divisors (29806567000).

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

21212031440 is a wasteful number, since it uses less digits than its factorization.

21212031440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9143159 (or 9143153 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

Adding to 21212031440 its reverse (4413021212), we get a palindrome (25625052652).

The spelling of 21212031440 in words is "twenty-one billion, two hundred twelve million, thirty-one thousand, four hundred forty".