21168213049 has 15 divisors (see below), whose sum is σ = 22051681723. Its totient is φ = 20320134352.

The previous prime is 21168213029. The next prime is 21168213113. The reversal of 21168213049 is 94031286112.

The square root of 21168213049 is 145493.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 7 ways, for example, as 1362717225 + 19805495824 = 36915^2 + 140732^2 .

It is not a de Polignac number, because 21168213049 - 2⁹ = 21168212537 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21168212999 and 21168213017.

It is not an unprimeable number, because it can be changed into a prime (21168213029) 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 14 ways as a sum of consecutive naturals, for example, 122359527 + ... + 122359699.

Almost surely, 2^21168213049 is an apocalyptic number.

21168213049 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21168213049 is the 145493-rd square number.

21168213049 is the 72747-th centered octagonal number.

It is an amenable number.

21168213049 is a deficient number, since it is larger than the sum of its proper divisors (883468674).

21168213049 is an frugal number, since it uses more digits than its factorization.

21168213049 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 462 (or 202 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 37.

Multiplying 21168213049 by its product of nonzero digits (20736), we get a square (438944065784064 = 20950992²).

The spelling of 21168213049 in words is "twenty-one billion, one hundred sixty-eight million, two hundred thirteen thousand, forty-nine".