21721443378 has 64 divisors (see below), whose sum is σ = 46846525440. Its totient is φ = 6692196672.

The previous prime is 21721443361. The next prime is 21721443379. The reversal of 21721443378 is 87334412712.

It is a super-2 number, since 2×21721443378² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21721443379) 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 31 ways as a sum of consecutive naturals, for example, 5473551 + ... + 5477517.

It is an arithmetic number, because the mean of its divisors is an integer number (731976960).

Almost surely, 2^21721443378 is an apocalyptic number.

21721443378 is an abundant number, since it is smaller than the sum of its proper divisors (25125082062).

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

21721443378 is a wasteful number, since it uses less digits than its factorization.

21721443378 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5151.

The product of its digits is 225792, while the sum is 42.

The spelling of 21721443378 in words is "twenty-one billion, seven hundred twenty-one million, four hundred forty-three thousand, three hundred seventy-eight".