19717985 has 16 divisors (see below), whose sum is σ = 27120000. Its totient is φ = 13481856.

The previous prime is 19717981. The next prime is 19717987. The reversal of 19717985 is 58971791.

It is a cyclic number.

It is not a de Polignac number, because 19717985 - 2² = 19717981 is a prime.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (19717981) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16901 + ... + 18029.

It is an arithmetic number, because the mean of its divisors is an integer number (1695000).

Almost surely, 2^19717985 is an apocalyptic number.

It is an amenable number.

19717985 is a deficient number, since it is larger than the sum of its proper divisors (7402015).

19717985 is a wasteful number, since it uses less digits than its factorization.

19717985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1640.

The product of its digits is 158760, while the sum is 47.

The square root of 19717985 is about 4440.4937788494. The cubic root of 19717985 is about 270.1598733093.

It can be divided in two parts, 19717 and 985, that added together give a palindrome (20702).

The spelling of 19717985 in words is "nineteen million, seven hundred seventeen thousand, nine hundred eighty-five".