1216745661 has 8 divisors (see below), whose sum is σ = 1646541664. Its totient is φ = 799056720.

The previous prime is 1216745659. The next prime is 1216745669. The reversal of 1216745661 is 1665476121.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1216745661 - 2¹ = 1216745659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216745669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3026530 + ... + 3026931.

It is an arithmetic number, because the mean of its divisors is an integer number (205817708).

Almost surely, 2^1216745661 is an apocalyptic number.

It is an amenable number.

1216745661 is a deficient number, since it is larger than the sum of its proper divisors (429796003).

1216745661 is an equidigital number, since it uses as much as digits as its factorization.

1216745661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6053531.

The product of its digits is 60480, while the sum is 39.

The square root of 1216745661 is about 34881.8815576224. The cubic root of 1216745661 is about 1067.5787862953.

The spelling of 1216745661 in words is "one billion, two hundred sixteen million, seven hundred forty-five thousand, six hundred sixty-one".