1221689 has 4 divisors (see below), whose sum is σ = 1396224. Its totient is φ = 1047156.

The previous prime is 1221667. The next prime is 1221707. The reversal of 1221689 is 9861221.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221689 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 (1221659) 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, 87257 + ... + 87270.

It is an arithmetic number, because the mean of its divisors is an integer number (349056).

2^1221689 is an apocalyptic number.

It is an amenable number.

1221689 is a deficient number, since it is larger than the sum of its proper divisors (174535).

1221689 is an equidigital number, since it uses as much as digits as its factorization.

1221689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174534.

The product of its digits is 1728, while the sum is 29.

The square root of 1221689 is about 1105.3004116529. The cubic root of 1221689 is about 106.9022602965.

The spelling of 1221689 in words is "one million, two hundred twenty-one thousand, six hundred eighty-nine".