99999999978 has 32 divisors (see below), whose sum is σ = 213135998976. Its totient is φ = 31205671728.

The previous prime is 99999999977. The next prime is 100000000003. The reversal of 99999999978 is 87999999999.

It is not an unprimeable number, because it can be changed into a prime (99999999977) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7702426 + ... + 7715397.

It is an arithmetic number, because the mean of its divisors is an integer number (6660499968).

Almost surely, 2^99999999978 is an apocalyptic number.

99999999978 is an abundant number, since it is smaller than the sum of its proper divisors (113135998998).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

99999999978 is a wasteful number, since it uses less digits than its factorization.

99999999978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15417898.

The product of its digits is 21695547384, while the sum is 96.

The spelling of 99999999978 in words is "ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred seventy-eight".