21342440 has 48 divisors (see below), whose sum is σ = 55865700. Its totient is φ = 7316736.

The previous prime is 21342437. The next prime is 21342443. The reversal of 21342440 is 4424312.

It is an interprime number because it is at equal distance from previous prime (21342437) and next prime (21342443).

It can be written as a sum of positive squares in 2 ways, for example, as 18472804 + 2869636 = 4298^2 + 1694^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21342443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3485 + ... + 7404.

Almost surely, 2^21342440 is an apocalyptic number.

21342440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21342440 is an abundant number, since it is smaller than the sum of its proper divisors (34523260).

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

21342440 is a wasteful number, since it uses less digits than its factorization.

21342440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10914 (or 10903 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 21342440 is about 4619.7878739180. The cubic root of 21342440 is about 277.3839679387.

Adding to 21342440 its reverse (4424312), we get a palindrome (25766752).

The spelling of 21342440 in words is "twenty-one million, three hundred forty-two thousand, four hundred forty".