1216601681 has 2 divisors, whose sum is σ = 1216601682. Its totient is φ = 1216601680.

The previous prime is 1216601677. The next prime is 1216601717. The reversal of 1216601681 is 1861066121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 745017025 + 471584656 = 27295^2 + 21716^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216601681 - 2² = 1216601677 is a prime.

It is a super-2 number, since 2×1216601681² = 2960239300424051522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1216601081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608300840 + 608300841.

It is an arithmetic number, because the mean of its divisors is an integer number (608300841).

Almost surely, 2^1216601681 is an apocalyptic number.

It is an amenable number.

1216601681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216601681 is an equidigital number, since it uses as much as digits as its factorization.

1216601681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 1216601681 is about 34879.8176744088. The cubic root of 1216601681 is about 1067.5366750412.

The spelling of 1216601681 in words is "one billion, two hundred sixteen million, six hundred one thousand, six hundred eighty-one".