21417840 has 120 divisors (see below), whose sum is σ = 72772128. Its totient is φ = 5644800.

The previous prime is 21417839. The next prime is 21417871. The reversal of 21417840 is 4871412.

It is a tau number, because it is divible by the number of its divisors (120).

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 108622 + ... + 108818.

Almost surely, 2^21417840 is an apocalyptic number.

21417840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21417840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36386064).

21417840 is an abundant number, since it is smaller than the sum of its proper divisors (51354288).

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

21417840 is a wasteful number, since it uses less digits than its factorization.

21417840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 367 (or 358 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 27.

The square root of 21417840 is about 4627.9412269388. The cubic root of 21417840 is about 277.7102375645.

The spelling of 21417840 in words is "twenty-one million, four hundred seventeen thousand, eight hundred forty".