21459840 has 64 divisors (see below), whose sum is σ = 68409360. Its totient is φ = 5722112.

The previous prime is 21459833. The next prime is 21459853. The reversal of 21459840 is 4895412.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

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, 3669 + ... + 7508.

Almost surely, 2^21459840 is an apocalyptic number.

21459840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21459840 is an abundant number, since it is smaller than the sum of its proper divisors (46949520).

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

21459840 is a wasteful number, since it uses less digits than its factorization.

21459840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11199 (or 11187 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 21459840 is about 4632.4766594123. The cubic root of 21459840 is about 277.8916473002.

The spelling of 21459840 in words is "twenty-one million, four hundred fifty-nine thousand, eight hundred forty".