20687931889 has 3 divisors (see below), whose sum is σ = 20688075723. Its totient is φ = 20687788056.

The previous prime is 20687931863. The next prime is 20687931893. The reversal of 20687931889 is 98813978602.

The square root of 20687931889 is 143833.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 12335434225 + 8352497664 = 111065^2 + 91392^2 .

It is not a de Polignac number, because 20687931889 - 2⁹ = 20687931377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20687931689) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 71917 + ... + 215749.

It is an arithmetic number, because the mean of its divisors is an integer number (6896025241).

Almost surely, 2^20687931889 is an apocalyptic number.

20687931889 is the 143833-rd square number.

20687931889 is the 71917-th centered octagonal number.

It is an amenable number.

20687931889 is a deficient number, since it is larger than the sum of its proper divisors (143834).

20687931889 is an frugal number, since it uses more digits than its factorization.

20687931889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287666 (or 143833 counting only the distinct ones).

The product of its (nonzero) digits is 10450944, while the sum is 61.

It can be divided in two parts, 20687 and 931889, that added together give a square (952576 = 976²).

The spelling of 20687931889 in words is "twenty billion, six hundred eighty-seven million, nine hundred thirty-one thousand, eight hundred eighty-nine".