15998981965 has 4 divisors (see below), whose sum is σ = 19198778364. Its totient is φ = 12799185568.

The previous prime is 15998981963. The next prime is 15998981989. The reversal of 15998981965 is 56918989951.

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 7953250761 + 8045731204 = 89181^2 + 89698^2 .

It is a cyclic number.

It is not a de Polignac number, because 15998981965 - 2¹ = 15998981963 is a prime.

It is a super-2 number, since 2×15998981965² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15998981894 and 15998981903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15998981963) 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, 1599898192 + ... + 1599898201.

It is an arithmetic number, because the mean of its divisors is an integer number (4799694591).

Almost surely, 2^15998981965 is an apocalyptic number.

It is an amenable number.

15998981965 is a deficient number, since it is larger than the sum of its proper divisors (3199796399).

15998981965 is an equidigital number, since it uses as much as digits as its factorization.

15998981965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3199796398.

The product of its digits is 62985600, while the sum is 70.

The spelling of 15998981965 in words is "fifteen billion, nine hundred ninety-eight million, nine hundred eighty-one thousand, nine hundred sixty-five".