21181309444 has 27 divisors (see below), whose sum is σ = 37807406623. Its totient is φ = 10383263072.

The previous prime is 21181309433. The next prime is 21181309489. The reversal of 21181309444 is 44490318112.

The square root of 21181309444 is 145538.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 13124451844 + 8056857600 = 114562^2 + 89760^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 15426342 + ... + 15427714.

Almost surely, 2^21181309444 is an apocalyptic number.

21181309444 is the 145538-th square number.

It is an amenable number.

21181309444 is a deficient number, since it is larger than the sum of its proper divisors (16626097179).

21181309444 is an frugal number, since it uses more digits than its factorization.

21181309444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2856 (or 1428 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 37.

It can be divided in two parts, 21181 and 309444, that added together give a square (330625 = 575²).

The spelling of 21181309444 in words is "twenty-one billion, one hundred eighty-one million, three hundred nine thousand, four hundred forty-four".