21617904 has 80 divisors (see below), whose sum is σ = 69638400. Its totient is φ = 5614080.

The previous prime is 21617899. The next prime is 21617909. The reversal of 21617904 is 40971612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21617899) and next prime (21617909).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21617909) 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 15 ways as a sum of consecutive naturals, for example, 772 + ... + 6620.

It is an arithmetic number, because the mean of its divisors is an integer number (870480).

Almost surely, 2^21617904 is an apocalyptic number.

21617904 is a gapful number since it is divisible by the number (24) 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 21617904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34819200).

21617904 is an abundant number, since it is smaller than the sum of its proper divisors (48020496).

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

21617904 is a wasteful number, since it uses less digits than its factorization.

21617904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5878 (or 5872 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 21617904 is about 4649.5057801878. The cubic root of 21617904 is about 278.5722559945.

The spelling of 21617904 in words is "twenty-one million, six hundred seventeen thousand, nine hundred four".