19987945 has 8 divisors (see below), whose sum is σ = 24031944. Its totient is φ = 15959424.

The previous prime is 19987907. The next prime is 19987949. The reversal of 19987945 is 54978991.

It can be written as a sum of positive squares in 4 ways, for example, as 2247001 + 17740944 = 1499^2 + 4212^2 .

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 19987945 - 2⁹ = 19987433 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19987892 and 19987901.

It is not an unprimeable number, because it can be changed into a prime (19987949) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 804 + ... + 6373.

It is an arithmetic number, because the mean of its divisors is an integer number (3003993).

Almost surely, 2^19987945 is an apocalyptic number.

It is an amenable number.

19987945 is a deficient number, since it is larger than the sum of its proper divisors (4043999).

19987945 is an equidigital number, since it uses as much as digits as its factorization.

19987945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7739.

The product of its digits is 816480, while the sum is 52.

The square root of 19987945 is about 4470.7879618698. The cubic root of 19987945 is about 271.3872135244.

The spelling of 19987945 in words is "nineteen million, nine hundred eighty-seven thousand, nine hundred forty-five".