1216661 has 4 divisors (see below), whose sum is σ = 1218924. Its totient is φ = 1214400.

The previous prime is 1216619. The next prime is 1216681. The reversal of 1216661 is 1666121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1666121 = 43 ⋅38747.

It can be written as a sum of positive squares in 2 ways, for example, as 372100 + 844561 = 610^2 + 919^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216661 - 2¹⁰ = 1215637 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 191 + ... + 1571.

It is an arithmetic number, because the mean of its divisors is an integer number (304731).

2^1216661 is an apocalyptic number.

It is an amenable number.

1216661 is a deficient number, since it is larger than the sum of its proper divisors (2263).

1216661 is an equidigital number, since it uses as much as digits as its factorization.

1216661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2262.

The product of its digits is 432, while the sum is 23.

The square root of 1216661 is about 1103.0235718243. The cubic root of 1216661 is about 106.7554025058.

The spelling of 1216661 in words is "one million, two hundred sixteen thousand, six hundred sixty-one".