7886987921 has 4 divisors (see below), whose sum is σ = 7887211812. Its totient is φ = 7886764032.

The previous prime is 7886987917. The next prime is 7886987923. The reversal of 7886987921 is 1297896887.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4724500225 + 3162487696 = 68735^2 + 56236^2 .

It is a cyclic number.

It is not a de Polignac number, because 7886987921 - 2² = 7886987917 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7886987923) 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, 46256 + ... + 133841.

It is an arithmetic number, because the mean of its divisors is an integer number (1971802953).

Almost surely, 2^7886987921 is an apocalyptic number.

It is an amenable number.

7886987921 is a deficient number, since it is larger than the sum of its proper divisors (223891).

7886987921 is a wasteful number, since it uses less digits than its factorization.

7886987921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223890.

The product of its digits is 24385536, while the sum is 65.

The square root of 7886987921 is about 88808.7153437094. The cubic root of 7886987921 is about 1990.5376291209.

The spelling of 7886987921 in words is "seven billion, eight hundred eighty-six million, nine hundred eighty-seven thousand, nine hundred twenty-one".