21445540 has 24 divisors (see below), whose sum is σ = 45581760. Its totient is φ = 8474208.

The previous prime is 21445537. The next prime is 21445573. The reversal of 21445540 is 4554412.

It is a happy number.

It is a super-2 number, since 2×21445540² = 919822371783200, which contains 22 as substring.

It is an unprimeable number.

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, 4800 + ... + 8119.

It is an arithmetic number, because the mean of its divisors is an integer number (1899240).

Almost surely, 2^21445540 is an apocalyptic number.

21445540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21445540 is an abundant number, since it is smaller than the sum of its proper divisors (24136220).

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

21445540 is a wasteful number, since it uses less digits than its factorization.

21445540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13011 (or 13009 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 25.

The square root of 21445540 is about 4630.9329513609. The cubic root of 21445540 is about 277.8299082013.

Adding to 21445540 its reverse (4554412), we get a palindrome (25999952).

It can be divided in two parts, 214 and 45540, that added together give a palindrome (45754).

The spelling of 21445540 in words is "twenty-one million, four hundred forty-five thousand, five hundred forty".