1221540 has 24 divisors (see below), whose sum is σ = 3420480. Its totient is φ = 325728.

The previous prime is 1221533. The next prime is 1221541. The reversal of 1221540 is 451221.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is not an unprimeable number, because it can be changed into a prime (1221541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10120 + ... + 10239.

It is an arithmetic number, because the mean of its divisors is an integer number (142520).

2^1221540 is an apocalyptic number.

1221540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221540 is an abundant number, since it is smaller than the sum of its proper divisors (2198940).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1221540 is a wasteful number, since it uses less digits than its factorization.

1221540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20371 (or 20369 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 1221540 is about 1105.2330071076. The cubic root of 1221540 is about 106.8979141047.

Adding to 1221540 its reverse (451221), we get a palindrome (1672761).

The spelling of 1221540 in words is "one million, two hundred twenty-one thousand, five hundred forty".