21112155531 has 24 divisors (see below), whose sum is σ = 30884162400. Its totient is φ = 13896446976.

The previous prime is 21112155511. The next prime is 21112155541. The reversal of 21112155531 is 13555121112.

It is a happy number.

21112155531 is a `hidden beast` number, since 2 + 1 + 1 + 121 + 5 + 5 + 531 = 666.

It is not a de Polignac number, because 21112155531 - 2¹⁰ = 21112154507 is a prime.

It is a super-2 number, since 2×21112155531² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21112155495 and 21112155504.

It is not an unprimeable number, because it can be changed into a prime (21112155511) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 176811 + ... + 271083.

It is an arithmetic number, because the mean of its divisors is an integer number (1286840100).

Almost surely, 2^21112155531 is an apocalyptic number.

21112155531 is a deficient number, since it is larger than the sum of its proper divisors (9772006869).

21112155531 is a wasteful number, since it uses less digits than its factorization.

21112155531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94595 (or 94592 counting only the distinct ones).

The product of its digits is 1500, while the sum is 27.

Adding to 21112155531 its reverse (13555121112), we get a palindrome (34667276643).

The spelling of 21112155531 in words is "twenty-one billion, one hundred twelve million, one hundred fifty-five thousand, five hundred thirty-one".