21221351440 has 20 divisors (see below), whose sum is σ = 49339642284. Its totient is φ = 8488540544.

The previous prime is 21221351423. The next prime is 21221351449. The reversal of 21221351440 is 4415312212.

It can be written as a sum of positive squares in 2 ways, for example, as 2476455696 + 18744895744 = 49764^2 + 136912^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (21221351449) 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 3 ways as a sum of consecutive naturals, for example, 132633367 + ... + 132633526.

Almost surely, 2^21221351440 is an apocalyptic number.

21221351440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221351440 is an abundant number, since it is smaller than the sum of its proper divisors (28118290844).

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

21221351440 is a wasteful number, since it uses less digits than its factorization.

21221351440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265266906 (or 265266900 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

Adding to 21221351440 its reverse (4415312212), we get a palindrome (25636663652).

The spelling of 21221351440 in words is "twenty-one billion, two hundred twenty-one million, three hundred fifty-one thousand, four hundred forty".