1216721 has 8 divisors (see below), whose sum is σ = 1353024. Its totient is φ = 1084720.

The previous prime is 1216717. The next prime is 1216729. The reversal of 1216721 is 1276121.

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

It is a cyclic number.

It is not a de Polignac number, because 1216721 - 2² = 1216717 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1216693 and 1216702.

It is not an unprimeable number, because it can be changed into a prime (1216729) 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, 461 + ... + 1626.

It is an arithmetic number, because the mean of its divisors is an integer number (169128).

2^1216721 is an apocalyptic number.

1216721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1216721 is a deficient number, since it is larger than the sum of its proper divisors (136303).

1216721 is a wasteful number, since it uses less digits than its factorization.

1216721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2151.

The product of its digits is 168, while the sum is 20.

The square root of 1216721 is about 1103.0507694571. The cubic root of 1216721 is about 106.7571573685.

The spelling of 1216721 in words is "one million, two hundred sixteen thousand, seven hundred twenty-one".