20871806138 has 4 divisors (see below), whose sum is σ = 31307709210. Its totient is φ = 10435903068.

The previous prime is 20871806129. The next prime is 20871806167. The reversal of 20871806138 is 83160817802.

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

It can be written as a sum of positive squares in only one way, i.e., 20863780249 + 8025889 = 144443^2 + 2833^2 .

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5217951533 + ... + 5217951536.

Almost surely, 2^20871806138 is an apocalyptic number.

20871806138 is a deficient number, since it is larger than the sum of its proper divisors (10435903072).

20871806138 is a wasteful number, since it uses less digits than its factorization.

20871806138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10435903071.

The product of its (nonzero) digits is 129024, while the sum is 44.

The spelling of 20871806138 in words is "twenty billion, eight hundred seventy-one million, eight hundred six thousand, one hundred thirty-eight".