21545440 has 48 divisors (see below), whose sum is σ = 58175712. Its totient is φ = 7386624.

The previous prime is 21545429. The next prime is 21545441. The reversal of 21545440 is 4454512.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545441) 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, 8499 + ... + 10738.

It is an arithmetic number, because the mean of its divisors is an integer number (1211994).

Almost surely, 2^21545440 is an apocalyptic number.

21545440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21545440 is an abundant number, since it is smaller than the sum of its proper divisors (36630272).

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

21545440 is a wasteful number, since it uses less digits than its factorization.

21545440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19259 (or 19251 counting only the distinct ones).

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

The square root of 21545440 is about 4641.7065827129. The cubic root of 21545440 is about 278.2606461162.

Adding to 21545440 its reverse (4454512), we get a palindrome (25999952).

The spelling of 21545440 in words is "twenty-one million, five hundred forty-five thousand, four hundred forty".