21057369946561 has 27 divisors (see below), whose sum is σ = 23347217164329. Its totient is φ = 18983222923392.

The previous prime is 21057369946447. The next prime is 21057369946567. The reversal of 21057369946561 is 16564996375012.

The square root of 21057369946561 is 4588831.

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

It can be written as a sum of positive squares in 4 ways, for example, as 13122759826225 + 7934610120336 = 3622535^2 + 2816844^2 .

It is not a de Polignac number, because 21057369946561 - 2²⁷ = 21057235728833 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21057369946493 and 21057369946502.

It is not an unprimeable number, because it can be changed into a prime (21057369946567) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 2565152425 + ... + 2565160633.

It is an arithmetic number, because the mean of its divisors is an integer number (864711746827).

Almost surely, 2^{21057369946561} is an apocalyptic number.

21057369946561 is the 4588831-st square number.

21057369946561 is the 2294416-th centered octagonal number.

It is an amenable number.

21057369946561 is a deficient number, since it is larger than the sum of its proper divisors (2289847217768).

21057369946561 is an frugal number, since it uses more digits than its factorization.

21057369946561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16530 (or 8265 counting only the distinct ones).

The product of its (nonzero) digits is 73483200, while the sum is 64.

The spelling of 21057369946561 in words is "twenty-one trillion, fifty-seven billion, three hundred sixty-nine million, nine hundred forty-six thousand, five hundred sixty-one".