691221 has 8 divisors (see below), whose sum is σ = 930240. Its totient is φ = 456512.

The previous prime is 691199. The next prime is 691231. The reversal of 691221 is 122196.

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 691221 - 2⁵ = 691189 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 691221.

It is not an unprimeable number, because it can be changed into a prime (691231) 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, 681 + ... + 1358.

It is an arithmetic number, because the mean of its divisors is an integer number (116280).

2⁶⁹¹²²¹ is an apocalyptic number.

It is an amenable number.

691221 is a deficient number, since it is larger than the sum of its proper divisors (239019).

691221 is a wasteful number, since it uses less digits than its factorization.

691221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2155.

The product of its digits is 216, while the sum is 21.

The square root of 691221 is about 831.3970170743. The cubic root of 691221 is about 88.4176513826.

The spelling of 691221 in words is "six hundred ninety-one thousand, two hundred twenty-one".