20521889161 has 4 divisors (see below), whose sum is σ = 21076534852. Its totient is φ = 19967243472.

The previous prime is 20521889131. The next prime is 20521889279. The reversal of 20521889161 is 16198812502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12809712400 + 7712176761 = 113180^2 + 87819^2 .

It is a cyclic number.

It is not a de Polignac number, because 20521889161 - 2¹⁹ = 20521364873 is a prime.

It is a super-2 number, since 2×20521889161² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20521889131) 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 3 ways as a sum of consecutive naturals, for example, 277322790 + ... + 277322863.

It is an arithmetic number, because the mean of its divisors is an integer number (5269133713).

Almost surely, 2^20521889161 is an apocalyptic number.

It is an amenable number.

20521889161 is a deficient number, since it is larger than the sum of its proper divisors (554645691).

20521889161 is an equidigital number, since it uses as much as digits as its factorization.

20521889161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 554645690.

The product of its (nonzero) digits is 69120, while the sum is 43.

The spelling of 20521889161 in words is "twenty billion, five hundred twenty-one million, eight hundred eighty-nine thousand, one hundred sixty-one".