999901100021 has 4 divisors (see below), whose sum is σ = 999926440044. Its totient is φ = 999875760000.

The previous prime is 999901100017. The next prime is 999901100057. The reversal of 999901100021 is 120001109999.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 161740708900 + 838160391121 = 402170^2 + 915511^2 .

It is a cyclic number.

It is not a de Polignac number, because 999901100021 - 2² = 999901100017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999901100621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12610730 + ... + 12689771.

It is an arithmetic number, because the mean of its divisors is an integer number (249981610011).

Almost surely, 2^999901100021 is an apocalyptic number.

It is an amenable number.

999901100021 is a deficient number, since it is larger than the sum of its proper divisors (25340023).

999901100021 is a wasteful number, since it uses less digits than its factorization.

999901100021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25340022.

The product of its (nonzero) digits is 13122, while the sum is 41.

The spelling of 999901100021 in words is "nine hundred ninety-nine billion, nine hundred one million, one hundred thousand, twenty-one".