1216441661 has 2 divisors, whose sum is σ = 1216441662. Its totient is φ = 1216441660.

The previous prime is 1216441621. The next prime is 1216441673. The reversal of 1216441661 is 1661446121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 679592761 + 536848900 = 26069^2 + 23170^2 .

It is an emirp because it is prime and its reverse (1661446121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1216441661 - 2²⁶ = 1149332797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1216441601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608220830 + 608220831.

It is an arithmetic number, because the mean of its divisors is an integer number (608220831).

Almost surely, 2^1216441661 is an apocalyptic number.

It is an amenable number.

1216441661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216441661 is an equidigital number, since it uses as much as digits as its factorization.

1216441661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 32.

The square root of 1216441661 is about 34877.5237223057. The cubic root of 1216441661 is about 1067.4898685113.

Adding to 1216441661 its reverse (1661446121), we get a palindrome (2877887782).

The spelling of 1216441661 in words is "one billion, two hundred sixteen million, four hundred forty-one thousand, six hundred sixty-one".