999308638021 has 4 divisors (see below), whose sum is σ = 999315156844. Its totient is φ = 999302119200.

The previous prime is 999308638001. The next prime is 999308638043. The reversal of 999308638021 is 120836803999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120836803999 = 3203 ⋅37726133.

It can be written as a sum of positive squares in 2 ways, for example, as 53719650625 + 945588987396 = 231775^2 + 972414^2 .

It is a 6-Lehmer number, since φ(999308638021) divides (999308638021-1)⁶.

It is a cyclic number.

It is not a de Polignac number, because 999308638021 - 2¹⁷ = 999308506949 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 (999308638001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3023790 + ... + 3337951.

It is an arithmetic number, because the mean of its divisors is an integer number (249828789211).

It is a Poulet number, since it divides 2^999308638020-1.

Almost surely, 2^999308638021 is an apocalyptic number.

It is an amenable number.

999308638021 is a deficient number, since it is larger than the sum of its proper divisors (6518823).

999308638021 is a wasteful number, since it uses less digits than its factorization.

999308638021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6518822.

The product of its (nonzero) digits is 5038848, while the sum is 58.

The spelling of 999308638021 in words is "nine hundred ninety-nine billion, three hundred eight million, six hundred thirty-eight thousand, twenty-one".