21171518738 has 4 divisors (see below), whose sum is σ = 31757278110. Its totient is φ = 10585759368.

The previous prime is 21171518713. The next prime is 21171518741. The reversal of 21171518738 is 83781517112.

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., 19885794289 + 1285724449 = 141017^2 + 35857^2 .

It is a super-3 number, since 3×21171518738³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5292879683 + ... + 5292879686.

Almost surely, 2^21171518738 is an apocalyptic number.

21171518738 is a deficient number, since it is larger than the sum of its proper divisors (10585759372).

21171518738 is a wasteful number, since it uses less digits than its factorization.

21171518738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10585759371.

The product of its digits is 94080, while the sum is 44.

The spelling of 21171518738 in words is "twenty-one billion, one hundred seventy-one million, five hundred eighteen thousand, seven hundred thirty-eight".