1221645 has 16 divisors (see below), whose sum is σ = 2040192. Its totient is φ = 623040.

The previous prime is 1221641. The next prime is 1221653. The reversal of 1221645 is 5461221.

It is not a de Polignac number, because 1221645 - 2² = 1221641 is a prime.

It is a super-3 number, since 3×1221645³ = 5469609487508733375, which contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221641) 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, 1426 + ... + 2115.

It is an arithmetic number, because the mean of its divisors is an integer number (127512).

2^1221645 is an apocalyptic number.

1221645 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1221645 is a deficient number, since it is larger than the sum of its proper divisors (818547).

1221645 is a wasteful number, since it uses less digits than its factorization.

1221645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3572.

The product of its digits is 480, while the sum is 21.

The square root of 1221645 is about 1105.2805073826. The cubic root of 1221645 is about 106.9009768941.

Adding to 1221645 its reverse (5461221), we get a palindrome (6682866).

The spelling of 1221645 in words is "one million, two hundred twenty-one thousand, six hundred forty-five".