21544540 has 12 divisors (see below), whose sum is σ = 45243576. Its totient is φ = 8617808.

The previous prime is 21544531. The next prime is 21544541. The reversal of 21544540 is 4544512.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21544541) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 538594 + ... + 538633.

It is an arithmetic number, because the mean of its divisors is an integer number (3770298).

Almost surely, 2^21544540 is an apocalyptic number.

21544540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21544540 is an abundant number, since it is smaller than the sum of its proper divisors (23699036).

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

21544540 is a wasteful number, since it uses less digits than its factorization.

21544540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1077236 (or 1077234 counting only the distinct ones).

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

The square root of 21544540 is about 4641.6096345988. The cubic root of 21544540 is about 278.2567715443.

The spelling of 21544540 in words is "twenty-one million, five hundred forty-four thousand, five hundred forty".