21317020 has 12 divisors (see below), whose sum is σ = 44765784. Its totient is φ = 8526800.

The previous prime is 21317017. The next prime is 21317027. The reversal of 21317020 is 2071312.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21316985 and 21317003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21317027) 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, 532906 + ... + 532945.

It is an arithmetic number, because the mean of its divisors is an integer number (3730482).

Almost surely, 2^21317020 is an apocalyptic number.

21317020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21317020 is an abundant number, since it is smaller than the sum of its proper divisors (23448764).

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

21317020 is a wasteful number, since it uses less digits than its factorization.

21317020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1065860 (or 1065858 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 21317020 is about 4617.0358456482. The cubic root of 21317020 is about 277.2737977531.

Adding to 21317020 its reverse (2071312), we get a palindrome (23388332).

The spelling of 21317020 in words is "twenty-one million, three hundred seventeen thousand, twenty".