21361849551 has 64 divisors (see below), whose sum is σ = 37374197760. Its totient is φ = 11800585440.

The previous prime is 21361849517. The next prime is 21361849559. The reversal of 21361849551 is 15594816312.

It is a happy number.

21361849551 is a `hidden beast` number, since 2 + 13 + 6 + 1 + 84 + 9 + 551 = 666.

It is not a de Polignac number, because 21361849551 - 2¹¹ = 21361847503 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21361849497 and 21361849506.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21361849559) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 10234630 + ... + 10236716.

It is an arithmetic number, because the mean of its divisors is an integer number (583971840).

Almost surely, 2^21361849551 is an apocalyptic number.

21361849551 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21361849551 is a deficient number, since it is larger than the sum of its proper divisors (16012348209).

21361849551 is a wasteful number, since it uses less digits than its factorization.

21361849551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3881 (or 3875 counting only the distinct ones).

The product of its digits is 259200, while the sum is 45.

It can be divided in two parts, 213618 and 49551, that added together give a square (263169 = 513²).

The spelling of 21361849551 in words is "twenty-one billion, three hundred sixty-one million, eight hundred forty-nine thousand, five hundred fifty-one".