1221657 has 4 divisors (see below), whose sum is σ = 1628880. Its totient is φ = 814436.

The previous prime is 1221653. The next prime is 1221659. The reversal of 1221657 is 7561221.

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 not a de Polignac number, because 1221657 - 2² = 1221653 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (1221653) 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, 203607 + ... + 203612.

It is an arithmetic number, because the mean of its divisors is an integer number (407220).

2^1221657 is an apocalyptic number.

It is an amenable number.

1221657 is a deficient number, since it is larger than the sum of its proper divisors (407223).

1221657 is an equidigital number, since it uses as much as digits as its factorization.

1221657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 407222.

The product of its digits is 840, while the sum is 24.

The square root of 1221657 is about 1105.2859358555. The cubic root of 1221657 is about 106.9013269160.

Adding to 1221657 its reverse (7561221), we get a palindrome (8782878).

The spelling of 1221657 in words is "one million, two hundred twenty-one thousand, six hundred fifty-seven".