21115431544 has 16 divisors (see below), whose sum is σ = 39596785200. Its totient is φ = 10556288832.

The previous prime is 21115431539. The next prime is 21115431563. The reversal of 21115431544 is 44513451112.

It is a super-2 number, since 2×21115431544² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 114117 + ... + 235060.

It is an arithmetic number, because the mean of its divisors is an integer number (2474799075).

Almost surely, 2^21115431544 is an apocalyptic number.

It is an amenable number.

21115431544 is a deficient number, since it is larger than the sum of its proper divisors (18481353656).

21115431544 is a wasteful number, since it uses less digits than its factorization.

21115431544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 356742 (or 356738 counting only the distinct ones).

The product of its digits is 9600, while the sum is 31.

Adding to 21115431544 its reverse (44513451112), we get a palindrome (65628882656).

The spelling of 21115431544 in words is "twenty-one billion, one hundred fifteen million, four hundred thirty-one thousand, five hundred forty-four".