1213663865 has 4 divisors (see below), whose sum is σ = 1456396644. Its totient is φ = 970931088.

The previous prime is 1213663861. The next prime is 1213663877. The reversal of 1213663865 is 5683663121.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 415996816 + 797667049 = 20396^2 + 28243^2 .

It is a cyclic number.

It is not a de Polignac number, because 1213663865 - 2² = 1213663861 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1213663861) 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, 121366382 + ... + 121366391.

It is an arithmetic number, because the mean of its divisors is an integer number (364099161).

Almost surely, 2^1213663865 is an apocalyptic number.

It is an amenable number.

1213663865 is a deficient number, since it is larger than the sum of its proper divisors (242732779).

1213663865 is an equidigital number, since it uses as much as digits as its factorization.

1213663865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 242732778.

The product of its digits is 155520, while the sum is 41.

The square root of 1213663865 is about 34837.6788118841. The cubic root of 1213663865 is about 1066.6766964660.

The spelling of 1213663865 in words is "one billion, two hundred thirteen million, six hundred sixty-three thousand, eight hundred sixty-five".