21056212161 has 12 divisors (see below), whose sum is σ = 30446862420. Its totient is φ = 14022551520.

The previous prime is 21056212159. The next prime is 21056212169. The reversal of 21056212161 is 16121265012.

21056212161 is a `hidden beast` number, since 2 + 10 + 5 + 621 + 21 + 6 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 9637152561 + 11419059600 = 98169^2 + 106860^2 .

It is not a de Polignac number, because 21056212161 - 2¹ = 21056212159 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21056212169) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1234666 + ... + 1251603.

It is an arithmetic number, because the mean of its divisors is an integer number (2537238535).

Almost surely, 2^21056212161 is an apocalyptic number.

It is an amenable number.

21056212161 is a deficient number, since it is larger than the sum of its proper divisors (9390650259).

21056212161 is a wasteful number, since it uses less digits than its factorization.

21056212161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2487216 (or 2487213 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

Adding to 21056212161 its reverse (16121265012), we get a palindrome (37177477173).

The spelling of 21056212161 in words is "twenty-one billion, fifty-six million, two hundred twelve thousand, one hundred sixty-one".