19999645 has 4 divisors (see below), whose sum is σ = 23999580. Its totient is φ = 15999712.

The previous prime is 19999631. The next prime is 19999663. The reversal of 19999645 is 54699991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54699991 = 6823 ⋅8017.

It can be written as a sum of positive squares in 2 ways, for example, as 8696601 + 11303044 = 2949^2 + 3362^2 .

It is a cyclic number.

It is not a de Polignac number, because 19999645 - 2¹¹ = 19997597 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 19999592 and 19999601.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1999960 + ... + 1999969.

It is an arithmetic number, because the mean of its divisors is an integer number (5999895).

Almost surely, 2^19999645 is an apocalyptic number.

It is an amenable number.

19999645 is a deficient number, since it is larger than the sum of its proper divisors (3999935).

19999645 is an equidigital number, since it uses as much as digits as its factorization.

19999645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3999934.

The product of its digits is 787320, while the sum is 52.

The square root of 19999645 is about 4472.0962646169. The cubic root of 19999645 is about 271.4401556196.

The spelling of 19999645 in words is "nineteen million, nine hundred ninety-nine thousand, six hundred forty-five".