9719999981 has 4 divisors (see below), whose sum is σ = 9720251100. Its totient is φ = 9719748864.

The previous prime is 9719999959. The next prime is 9720000007. The reversal of 9719999981 is 1899999179.

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 553660900 + 9166339081 = 23530^2 + 95741^2 .

It is a cyclic number.

It is not a de Polignac number, because 9719999981 - 2¹⁰ = 9719998957 is a prime.

It is a super-2 number, since 2×9719999981² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9719999381) 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, 53846 + ... + 149463.

It is an arithmetic number, because the mean of its divisors is an integer number (2430062775).

Almost surely, 2^9719999981 is an apocalyptic number.

It is an amenable number.

9719999981 is a deficient number, since it is larger than the sum of its proper divisors (251119).

9719999981 is a wasteful number, since it uses less digits than its factorization.

9719999981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251118.

The product of its digits is 29760696, while the sum is 71.

The square root of 9719999981 is about 98590.0602545713. The cubic root of 9719999981 is about 2134.1359813035.

The spelling of 9719999981 in words is "nine billion, seven hundred nineteen million, nine hundred ninety-nine thousand, nine hundred eighty-one".