21520404244 has 12 divisors (see below), whose sum is σ = 39876043284. Its totient is φ = 10127249024.

The previous prime is 21520404233. The next prime is 21520404263. The reversal of 21520404244 is 44240402512.

It can be written as a sum of positive squares in 2 ways, for example, as 19582643844 + 1937760400 = 139938^2 + 44020^2 .

It is a super-3 number, since 3×21520404244³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 158238199 + ... + 158238334.

It is an arithmetic number, because the mean of its divisors is an integer number (3323003607).

Almost surely, 2^21520404244 is an apocalyptic number.

It is an amenable number.

21520404244 is a deficient number, since it is larger than the sum of its proper divisors (18355639040).

21520404244 is a wasteful number, since it uses less digits than its factorization.

21520404244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316476554 (or 316476552 counting only the distinct ones).

The product of its (nonzero) digits is 10240, while the sum is 28.

Adding to 21520404244 its reverse (44240402512), we get a palindrome (65760806756).

The spelling of 21520404244 in words is "twenty-one billion, five hundred twenty million, four hundred four thousand, two hundred forty-four".