20961847284921 has 81 divisors (see below), whose sum is σ = 32669178120111. Its totient is φ = 12949797436128.

The previous prime is 20961847284907. The next prime is 20961847285003. The reversal of 20961847284921 is 12948274816902.

The square root of 20961847284921 is 4578411.

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

20961847284921 is a `hidden beast` number, since 2 + 0 + 9 + 61 + 8 + 472 + 84 + 9 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 3940776849321 + 17021070435600 = 1985139^2 + 4125660^2 .

It is not a de Polignac number, because 20961847284921 - 2²¹ = 20961845187769 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20961847184921) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 12265562215 + ... + 12265563923.

Almost surely, 2^{20961847284921} is an apocalyptic number.

20961847284921 is the 4578411-st square number.

20961847284921 is the 2289206-th centered octagonal number.

It is an amenable number.

20961847284921 is a deficient number, since it is larger than the sum of its proper divisors (11707330835190).

20961847284921 is an frugal number, since it uses more digits than its factorization.

20961847284921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3556 (or 1778 counting only the distinct ones).

The product of its (nonzero) digits is 27869184, while the sum is 63.

The spelling of 20961847284921 in words is "twenty trillion, nine hundred sixty-one billion, eight hundred forty-seven million, two hundred eighty-four thousand, nine hundred twenty-one".