7911988421 has 4 divisors (see below), whose sum is σ = 7913757792. Its totient is φ = 7910219052.

The previous prime is 7911988397. The next prime is 7911988429. The reversal of 7911988421 is 1248891197.

It is a happy number.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1248891197 = 157 ⋅7954721.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7911988421 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 7911988421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7911988429) 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, 877961 + ... + 886926.

It is an arithmetic number, because the mean of its divisors is an integer number (1978439448).

Almost surely, 2^7911988421 is an apocalyptic number.

It is an amenable number.

7911988421 is a deficient number, since it is larger than the sum of its proper divisors (1769371).

7911988421 is a wasteful number, since it uses less digits than its factorization.

7911988421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1769370.

The product of its digits is 290304, while the sum is 50.

The square root of 7911988421 is about 88949.3587441753. The cubic root of 7911988421 is about 1992.6386401833.

The spelling of 7911988421 in words is "seven billion, nine hundred eleven million, nine hundred eighty-eight thousand, four hundred twenty-one".