1221765 has 16 divisors (see below), whose sum is σ = 1997568. Its totient is φ = 637376.

The previous prime is 1221761. The next prime is 1221767. The reversal of 1221765 is 5671221.

It is a cyclic number.

It is not a de Polignac number, because 1221765 - 2² = 1221761 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221761) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 162 + ... + 1571.

It is an arithmetic number, because the mean of its divisors is an integer number (124848).

2^1221765 is an apocalyptic number.

1221765 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1221765 is a deficient number, since it is larger than the sum of its proper divisors (775803).

1221765 is a wasteful number, since it uses less digits than its factorization.

1221765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1788.

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

The square root of 1221765 is about 1105.3347909118. The cubic root of 1221765 is about 106.9044770100.

Adding to 1221765 its reverse (5671221), we get a palindrome (6892986).

The spelling of 1221765 in words is "one million, two hundred twenty-one thousand, seven hundred sixty-five".