21445380 has 72 divisors (see below), whose sum is σ = 70971264. Its totient is φ = 5198400.

The previous prime is 21445373. The next prime is 21445387. The reversal of 21445380 is 8354412.

It is an interprime number because it is at equal distance from previous prime (21445373) and next prime (21445387).

It is not an unprimeable number, because it can be changed into a prime (21445387) 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 23 ways as a sum of consecutive naturals, for example, 3436 + ... + 7395.

It is an arithmetic number, because the mean of its divisors is an integer number (985712).

Almost surely, 2^21445380 is an apocalyptic number.

21445380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21445380 is an abundant number, since it is smaller than the sum of its proper divisors (49525884).

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

21445380 is a wasteful number, since it uses less digits than its factorization.

21445380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10857 (or 10852 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21445380 is about 4630.9156761919. The cubic root of 21445380 is about 277.8292172589.

Adding to 21445380 its reverse (8354412), we get a palindrome (29799792).

The spelling of 21445380 in words is "twenty-one million, four hundred forty-five thousand, three hundred eighty".