9999981391 has 8 divisors (see below), whose sum is σ = 10035702144. Its totient is φ = 9964284120.

The previous prime is 9999981373. The next prime is 9999981473. The reversal of 9999981391 is 1931899999.

9999981391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 9999981391 - 2⁵ = 9999981359 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 (9999981091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1552720 + ... + 1559146.

It is an arithmetic number, because the mean of its divisors is an integer number (1254462768).

Almost surely, 2^9999981391 is an apocalyptic number.

9999981391 is a deficient number, since it is larger than the sum of its proper divisors (35720753).

9999981391 is a wasteful number, since it uses less digits than its factorization.

9999981391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11741.

The product of its digits is 12754584, while the sum is 67.

The square root of 9999981391 is about 99999.9069549567. The cubic root of 9999981391 is about 2154.4333536352.

The spelling of 9999981391 in words is "nine billion, nine hundred ninety-nine million, nine hundred eighty-one thousand, three hundred ninety-one".