9987778994 has 4 divisors (see below), whose sum is σ = 14981668494. Its totient is φ = 4993889496.

The previous prime is 9987778979. The next prime is 9987779023. The reversal of 9987778994 is 4998777899.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 4998777899 = 617 ⋅8101747.

It can be written as a sum of positive squares in only one way, i.e., 5092677769 + 4895101225 = 71363^2 + 69965^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2496944747 + ... + 2496944750.

Almost surely, 2^9987778994 is an apocalyptic number.

9987778994 is a deficient number, since it is larger than the sum of its proper divisors (4993889500).

9987778994 is a wasteful number, since it uses less digits than its factorization.

9987778994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4993889499.

The product of its digits is 576108288, while the sum is 77.

The square root of 9987778994 is about 99938.8762894600. The cubic root of 9987778994 is about 2153.5566869562.

It can be divided in two parts, 99877 and 78994, that added together give a palindrome (178871).

The spelling of 9987778994 in words is "nine billion, nine hundred eighty-seven million, seven hundred seventy-eight thousand, nine hundred ninety-four".