999688644 has 36 divisors (see below), whose sum is σ = 2595291244. Its totient is φ = 324222912.

The previous prime is 999688643. The next prime is 999688649. The reversal of 999688644 is 446886999.

It can be written as a sum of positive squares in 2 ways, for example, as 620607744 + 379080900 = 24912^2 + 19470^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is not an unprimeable number, because it can be changed into a prime (999688643) 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, 373927 + ... + 376590.

Almost surely, 2^999688644 is an apocalyptic number.

It is an amenable number.

999688644 is an abundant number, since it is smaller than the sum of its proper divisors (1595602600).

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

999688644 is a wasteful number, since it uses less digits than its factorization.

999688644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 750564 (or 750559 counting only the distinct ones).

The product of its digits is 26873856, while the sum is 63.

The square root of 999688644 is about 31617.8532478092. The cubic root of 999688644 is about 999.8962038934.

The spelling of 999688644 in words is "nine hundred ninety-nine million, six hundred eighty-eight thousand, six hundred forty-four".