21845240 has 32 divisors (see below), whose sum is σ = 49518000. Its totient is φ = 8673024.

The previous prime is 21845237. The next prime is 21845249. The reversal of 21845240 is 4254812.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21845249) 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 7 ways as a sum of consecutive naturals, for example, 3596 + ... + 7524.

Almost surely, 2^21845240 is an apocalyptic number.

21845240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21845240 is an abundant number, since it is smaller than the sum of its proper divisors (27672760).

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

21845240 is a wasteful number, since it uses less digits than its factorization.

21845240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4079 (or 4075 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 26.

The square root of 21845240 is about 4673.8891728410. The cubic root of 21845240 is about 279.5453505990.

The spelling of 21845240 in words is "twenty-one million, eight hundred forty-five thousand, two hundred forty".