999998640 has 60 divisors (see below), whose sum is σ = 3358331184. Its totient is φ = 266666112.

The previous prime is 999998639. The next prime is 999998641. The reversal of 999998640 is 46899999.

999998640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (999998639) and next prime (999998641).

It is a tau number, because it is divible by the number of its divisors (60).

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (999998641) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 693724 + ... + 695163.

Almost surely, 2^999998640 is an apocalyptic number.

999998640 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

999998640 is an abundant number, since it is smaller than the sum of its proper divisors (2358332544).

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

999998640 is a wasteful number, since it uses less digits than its factorization.

999998640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1388906 (or 1388897 counting only the distinct ones).

The product of its (nonzero) digits is 11337408, while the sum is 63.

The square root of 999998640 is about 31622.7550981884. The cubic root of 999998640 is about 999.9995466665. Note that the first 3 decimals are identical.

The spelling of 999998640 in words is "nine hundred ninety-nine million, nine hundred ninety-eight thousand, six hundred forty".