1561217217 has 16 divisors (see below), whose sum is σ = 2379604992. Its totient is φ = 891896400.

The previous prime is 1561217149. The next prime is 1561217227. The reversal of 1561217217 is 7127121651.

It is not a de Polignac number, because 1561217217 - 2¹¹ = 1561215169 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1561217227) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 109342 + ... + 122792.

It is an arithmetic number, because the mean of its divisors is an integer number (148725312).

Almost surely, 2^1561217217 is an apocalyptic number.

It is an amenable number.

1561217217 is a deficient number, since it is larger than the sum of its proper divisors (818387775).

1561217217 is a wasteful number, since it uses less digits than its factorization.

1561217217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18988.

The product of its digits is 5880, while the sum is 33.

The square root of 1561217217 is about 39512.2413563189. The cubic root of 1561217217 is about 1160.0795667281.

Adding to 1561217217 its reverse (7127121651), we get a palindrome (8688338868).

The spelling of 1561217217 in words is "one billion, five hundred sixty-one million, two hundred seventeen thousand, two hundred seventeen".