999661539864 has 256 divisors, whose sum is σ = 3056313254400. Its totient is φ = 269082058752.

The previous prime is 999661539827. The next prime is 999661539869. The reversal of 999661539864 is 468935166999.

It is a super-2 number, since 2×999661539864² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999661539869) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5247547 + ... + 5434709.

It is an arithmetic number, because the mean of its divisors is an integer number (11938723650).

Almost surely, 2^999661539864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 999661539864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1528156627200).

999661539864 is an abundant number, since it is smaller than the sum of its proper divisors (2056651714536).

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

999661539864 is a wasteful number, since it uses less digits than its factorization.

999661539864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187274 (or 187270 counting only the distinct ones).

The product of its digits is 680244480, while the sum is 75.

The spelling of 999661539864 in words is "nine hundred ninety-nine billion, six hundred sixty-one million, five hundred thirty-nine thousand, eight hundred sixty-four".