19991245 has 4 divisors (see below), whose sum is σ = 23989500. Its totient is φ = 15992992.

The previous prime is 19991243. The next prime is 19991267. The reversal of 19991245 is 54219991.

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 3164841 + 16826404 = 1779^2 + 4102^2 .

It is a cyclic number.

It is not a de Polignac number, because 19991245 - 2¹ = 19991243 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 19991198 and 19991207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19991243) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1999120 + ... + 1999129.

It is an arithmetic number, because the mean of its divisors is an integer number (5997375).

Almost surely, 2^19991245 is an apocalyptic number.

It is an amenable number.

19991245 is a deficient number, since it is larger than the sum of its proper divisors (3998255).

19991245 is an equidigital number, since it uses as much as digits as its factorization.

19991245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3998254.

The product of its digits is 29160, while the sum is 40.

The square root of 19991245 is about 4471.1570090973. The cubic root of 19991245 is about 271.4021480016.

The spelling of 19991245 in words is "nineteen million, nine hundred ninety-one thousand, two hundred forty-five".