20897882721 has 9 divisors (see below), whose sum is σ = 30186457041. Its totient is φ = 13931632692.

The previous prime is 20897882713. The next prime is 20897882743. The reversal of 20897882721 is 12728879802.

The square root of 20897882721 is 144561.

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

20897882721 is a `hidden beast` number, since 208 + 97 + 88 + 272 + 1 = 666.

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 20897882721 - 2³ = 20897882713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20897832721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 409590 + ... + 457776.

Almost surely, 2^20897882721 is an apocalyptic number.

20897882721 is the 144561-st square number.

20897882721 is the 72281-st centered octagonal number.

It is an amenable number.

20897882721 is a deficient number, since it is larger than the sum of its proper divisors (9288574320).

20897882721 is an frugal number, since it uses more digits than its factorization.

20897882721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96380 (or 48190 counting only the distinct ones).

The product of its (nonzero) digits is 1806336, while the sum is 54.

The spelling of 20897882721 in words is "twenty billion, eight hundred ninety-seven million, eight hundred eighty-two thousand, seven hundred twenty-one".