1221664 has 12 divisors (see below), whose sum is σ = 2405214. Its totient is φ = 610816.

The previous prime is 1221659. The next prime is 1221667. The reversal of 1221664 is 4661221.

It can be written as a sum of positive squares in only one way, i.e., 1210000 + 11664 = 1100^2 + 108^2 .

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (1221667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19057 + ... + 19120.

2^1221664 is an apocalyptic number.

It is an amenable number.

1221664 is a deficient number, since it is larger than the sum of its proper divisors (1183550).

1221664 is an equidigital number, since it uses as much as digits as its factorization.

1221664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38187 (or 38179 counting only the distinct ones).

The product of its digits is 576, while the sum is 22.

The square root of 1221664 is about 1105.2891024524. The cubic root of 1221664 is about 106.9015310944.

Adding to 1221664 its reverse (4661221), we get a palindrome (5882885).

The spelling of 1221664 in words is "one million, two hundred twenty-one thousand, six hundred sixty-four".