21417520 has 20 divisors (see below), whose sum is σ = 49795920. Its totient is φ = 8566976.

The previous prime is 21417509. The next prime is 21417523. The reversal of 21417520 is 2571412.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 21417491 and 21417500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21417523) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 133780 + ... + 133939.

It is an arithmetic number, because the mean of its divisors is an integer number (2489796).

Almost surely, 2^21417520 is an apocalyptic number.

21417520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21417520 is an abundant number, since it is smaller than the sum of its proper divisors (28378400).

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

21417520 is a wasteful number, since it uses less digits than its factorization.

21417520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267732 (or 267726 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 21417520 is about 4627.9066542012. The cubic root of 21417520 is about 277.7088544851.

Adding to 21417520 its reverse (2571412), we get a palindrome (23988932).

It can be divided in two parts, 21417 and 520, that multiplied together give a triangular number (11136840 = T₄₇₁₉).

The spelling of 21417520 in words is "twenty-one million, four hundred seventeen thousand, five hundred twenty".