12215540 has 24 divisors (see below), whose sum is σ = 26280072. Its totient is φ = 4766720.

The previous prime is 12215531. The next prime is 12215543. The reversal of 12215540 is 4551221.

It can be written as a sum of positive squares in 4 ways, for example, as 1073296 + 11142244 = 1036^2 + 3338^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12215543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6629 + ... + 8268.

It is an arithmetic number, because the mean of its divisors is an integer number (1095003).

Almost surely, 2^12215540 is an apocalyptic number.

12215540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

12215540 is an abundant number, since it is smaller than the sum of its proper divisors (14064532).

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

12215540 is a wasteful number, since it uses less digits than its factorization.

12215540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14947 (or 14945 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 12215540 is about 3495.0736759044. The cubic root of 12215540 is about 230.3054542716.

Adding to 12215540 its reverse (4551221), we get a palindrome (16766761).

The spelling of 12215540 in words is "twelve million, two hundred fifteen thousand, five hundred forty".