21445340 has 72 divisors (see below), whose sum is σ = 53242560. Its totient is φ = 7233408.

The previous prime is 21445331. The next prime is 21445349. The reversal of 21445340 is 4354412.

It is an interprime number because it is at equal distance from previous prime (21445331) and next prime (21445349).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21445349) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 77282 + ... + 77558.

It is an arithmetic number, because the mean of its divisors is an integer number (739480).

Almost surely, 2^21445340 is an apocalyptic number.

21445340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21445340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26621280).

21445340 is an abundant number, since it is smaller than the sum of its proper divisors (31797220).

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

21445340 is a wasteful number, since it uses less digits than its factorization.

21445340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 379 (or 370 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 23.

The square root of 21445340 is about 4630.9113573896. The cubic root of 21445340 is about 277.8290445228.

Adding to 21445340 its reverse (4354412), we get a palindrome (25799752).

It can be divided in two parts, 214 and 45340, that added together give a palindrome (45554).

The spelling of 21445340 in words is "twenty-one million, four hundred forty-five thousand, three hundred forty".