999440640 has 432 divisors, whose sum is σ = 3914668800. Its totient is φ = 241274880.

The previous prime is 999440639. The next prime is 999440677. The reversal of 999440640 is 46044999.

It is a tau number, because it is divible by the number of its divisors (432).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4181641 + ... + 4181879.

Almost surely, 2^999440640 is an apocalyptic number.

999440640 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 999440640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1957334400).

999440640 is an abundant number, since it is smaller than the sum of its proper divisors (2915228160).

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

999440640 is a wasteful number, since it uses less digits than its factorization.

999440640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291 (or 260 counting only the distinct ones).

The product of its (nonzero) digits is 279936, while the sum is 45.

The square root of 999440640 is about 31613.9311063967. The cubic root of 999440640 is about 999.8135118910.

The spelling of 999440640 in words is "nine hundred ninety-nine million, four hundred forty thousand, six hundred forty".