21531223044 has 72 divisors (see below), whose sum is σ = 58048551288. Its totient is φ = 6705561600.

The previous prime is 21531223037. The next prime is 21531223057. The reversal of 21531223044 is 44032213512.

It can be written as a sum of positive squares in 4 ways, for example, as 3281914944 + 18249308100 = 57288^2 + 135090^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21531222999 and 21531223017.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 44557 + ... + 212244.

It is an arithmetic number, because the mean of its divisors is an integer number (806229879).

Almost surely, 2^21531223044 is an apocalyptic number.

It is an amenable number.

21531223044 is an abundant number, since it is smaller than the sum of its proper divisors (36517328244).

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

21531223044 is a wasteful number, since it uses less digits than its factorization.

21531223044 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256965 (or 256960 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

Adding to 21531223044 its reverse (44032213512), we get a palindrome (65563436556).

The spelling of 21531223044 in words is "twenty-one billion, five hundred thirty-one million, two hundred twenty-three thousand, forty-four".