21457540 has 24 divisors (see below), whose sum is σ = 48527640. Its totient is φ = 7922688.

The previous prime is 21457523. The next prime is 21457603. The reversal of 21457540 is 4575412.

It can be written as a sum of positive squares in 4 ways, for example, as 2116 + 21455424 = 46^2 + 4632^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21457499 and 21457508.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 41005 + ... + 41524.

It is an arithmetic number, because the mean of its divisors is an integer number (2021985).

Almost surely, 2^21457540 is an apocalyptic number.

21457540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21457540 is an abundant number, since it is smaller than the sum of its proper divisors (27070100).

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

21457540 is a wasteful number, since it uses less digits than its factorization.

21457540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82551 (or 82549 counting only the distinct ones).

The product of its (nonzero) digits is 5600, while the sum is 28.

The square root of 21457540 is about 4632.2284054222. The cubic root of 21457540 is about 277.8817190867.

The spelling of 21457540 in words is "twenty-one million, four hundred fifty-seven thousand, five hundred forty".