8128721138 has 8 divisors (see below), whose sum is σ = 12194375088. Its totient is φ = 4063929444.

The previous prime is 8128721129. The next prime is 8128721143. The reversal of 8128721138 is 8311278218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×8128721138² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 8128721095 and 8128721104.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 191456 + ... + 230027.

It is an arithmetic number, because the mean of its divisors is an integer number (1524296886).

Almost surely, 2^8128721138 is an apocalyptic number.

8128721138 is a deficient number, since it is larger than the sum of its proper divisors (4065653950).

8128721138 is a wasteful number, since it uses less digits than its factorization.

8128721138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 431128.

The product of its digits is 43008, while the sum is 41.

The square root of 8128721138 is about 90159.4206835869. The cubic root of 8128721138 is about 2010.6697386157.

The spelling of 8128721138 in words is "eight billion, one hundred twenty-eight million, seven hundred twenty-one thousand, one hundred thirty-eight".