999780012100 has 27 divisors (see below), whose sum is σ = 2169544324087. Its totient is φ = 399908005280.

The previous prime is 999780012037. The next prime is 999780012107. The reversal of 999780012100 is 1210087999.

It is a happy number.

The square root of 999780012100 is 999890.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 583228525636 + 416551486464 = 763694^2 + 645408^2 .

It is a super-2 number, since 2×999780012100² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (999780012107) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 9948906 + ... + 10048894.

Almost surely, 2^999780012100 is an apocalyptic number.

999780012100 is the 999890-th square number.

It is an amenable number.

999780012100 is an abundant number, since it is smaller than the sum of its proper divisors (1169764311987).

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

999780012100 is an frugal number, since it uses more digits than its factorization.

999780012100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199992 (or 99996 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 46.

The spelling of 999780012100 in words is "nine hundred ninety-nine billion, seven hundred eighty million, twelve thousand, one hundred".