7839978121 has 4 divisors (see below), whose sum is σ = 7855690000. Its totient is φ = 7824266244.

The previous prime is 7839978101. The next prime is 7839978131. The reversal of 7839978121 is 1218799387.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 7839978121 - 2¹¹ = 7839976073 is a prime.

It is a super-2 number, since 2×7839978121² (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 (7839978101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7855191 + ... + 7856188.

It is an arithmetic number, because the mean of its divisors is an integer number (1963922500).

Almost surely, 2^7839978121 is an apocalyptic number.

It is an amenable number.

7839978121 is a deficient number, since it is larger than the sum of its proper divisors (15711879).

7839978121 is a wasteful number, since it uses less digits than its factorization.

7839978121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15711878.

The product of its digits is 1524096, while the sum is 55.

The square root of 7839978121 is about 88543.6509355696. The cubic root of 7839978121 is about 1986.5749287843.

It can be divided in two parts, 78399 and 78121, that added together give a triangular number (156520 = T₅₅₉).

The spelling of 7839978121 in words is "seven billion, eight hundred thirty-nine million, nine hundred seventy-eight thousand, one hundred twenty-one".