1691221 has 4 divisors (see below), whose sum is σ = 1932832. Its totient is φ = 1449612.

The previous prime is 1691219. The next prime is 1691227. The reversal of 1691221 is 1221961.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1221961 = 13 ⋅93997.

It is a cyclic number.

It is not a de Polignac number, because 1691221 - 2¹ = 1691219 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1691192 and 1691201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1691227) 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, 120795 + ... + 120808.

It is an arithmetic number, because the mean of its divisors is an integer number (483208).

2^1691221 is an apocalyptic number.

It is an amenable number.

1691221 is a deficient number, since it is larger than the sum of its proper divisors (241611).

1691221 is an equidigital number, since it uses as much as digits as its factorization.

1691221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241610.

The product of its digits is 216, while the sum is 22.

The square root of 1691221 is about 1300.4695305927. The cubic root of 1691221 is about 119.1425216104.

The spelling of 1691221 in words is "one million, six hundred ninety-one thousand, two hundred twenty-one".