999987778 has 4 divisors (see below), whose sum is σ = 1499981670. Its totient is φ = 499993888.

The previous prime is 999987763. The next prime is 999987829. The reversal of 999987778 is 877789999.

999987778 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 877789999 = 103 ⋅8522233.

It can be written as a sum of positive squares in only one way, i.e., 990172089 + 9815689 = 31467^2 + 3133^2 .

It is a super-2 number, since 2×999987778² = 1999951112298754568, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 999987778.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 249996943 + ... + 249996946.

Almost surely, 2^999987778 is an apocalyptic number.

999987778 is a deficient number, since it is larger than the sum of its proper divisors (499993892).

999987778 is a wasteful number, since it uses less digits than its factorization.

999987778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499993891.

The product of its digits is 144027072, while the sum is 73.

The square root of 999987778 is about 31622.5833543055. The cubic root of 999987778 is about 999.9959259834.

The spelling of 999987778 in words is "nine hundred ninety-nine million, nine hundred eighty-seven thousand, seven hundred seventy-eight".