1216721671 has 16 divisors (see below), whose sum is σ = 1417052448. Its totient is φ = 1041025920.

The previous prime is 1216721663. The next prime is 1216721683. The reversal of 1216721671 is 1761276121.

It is not a de Polignac number, because 1216721671 - 2³ = 1216721663 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 (1216721641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4260 + ... + 49513.

It is an arithmetic number, because the mean of its divisors is an integer number (88565778).

Almost surely, 2^1216721671 is an apocalyptic number.

1216721671 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1216721671 is a deficient number, since it is larger than the sum of its proper divisors (200330777).

1216721671 is an equidigital number, since it uses as much as digits as its factorization.

1216721671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53823 (or 53801 counting only the distinct ones).

The product of its digits is 7056, while the sum is 34.

The square root of 1216721671 is about 34881.5376811287. The cubic root of 1216721671 is about 1067.5717699335.

Adding to 1216721671 its reverse (1761276121), we get a palindrome (2977997792).

The spelling of 1216721671 in words is "one billion, two hundred sixteen million, seven hundred twenty-one thousand, six hundred seventy-one".