1216571321 has 4 divisors (see below), whose sum is σ = 1390367232. Its totient is φ = 1042775412.

The previous prime is 1216571309. The next prime is 1216571383. The reversal of 1216571321 is 1231756121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1216571321 - 2¹⁰ = 1216570297 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1216571621) 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, 86897945 + ... + 86897958.

It is an arithmetic number, because the mean of its divisors is an integer number (347591808).

Almost surely, 2^1216571321 is an apocalyptic number.

It is an amenable number.

1216571321 is a deficient number, since it is larger than the sum of its proper divisors (173795911).

1216571321 is an equidigital number, since it uses as much as digits as its factorization.

1216571321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173795910.

The product of its digits is 2520, while the sum is 29.

The square root of 1216571321 is about 34879.3824629967. The cubic root of 1216571321 is about 1067.5277949277.

The spelling of 1216571321 in words is "one billion, two hundred sixteen million, five hundred seventy-one thousand, three hundred twenty-one".