21344240 has 40 divisors (see below), whose sum is σ = 49818240. Its totient is φ = 8504576.

The previous prime is 21344237. The next prime is 21344243. The reversal of 21344240 is 4244312.

It is an interprime number because it is at equal distance from previous prime (21344237) and next prime (21344243).

It is a tau number, because it is divible by the number of its divisors (40).

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 (21344243) 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, 38042 + ... + 38598.

It is an arithmetic number, because the mean of its divisors is an integer number (1245456).

Almost surely, 2^21344240 is an apocalyptic number.

21344240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21344240 is an abundant number, since it is smaller than the sum of its proper divisors (28474000).

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

21344240 is a wasteful number, since it uses less digits than its factorization.

21344240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1049 (or 1043 counting only the distinct ones).

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

The square root of 21344240 is about 4619.9826839502. The cubic root of 21344240 is about 277.3917658148.

Adding to 21344240 its reverse (4244312), we get a palindrome (25588552).

The spelling of 21344240 in words is "twenty-one million, three hundred forty-four thousand, two hundred forty".