21211704 has 48 divisors (see below), whose sum is σ = 59950800. Its totient is φ = 6762624.

The previous prime is 21211643. The next prime is 21211709. The reversal of 21211704 is 40711212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211709) 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 11 ways as a sum of consecutive naturals, for example, 4749 + ... + 8060.

It is an arithmetic number, because the mean of its divisors is an integer number (1248975).

Almost surely, 2^21211704 is an apocalyptic number.

21211704 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21211704 is an abundant number, since it is smaller than the sum of its proper divisors (38739096).

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

21211704 is a wasteful number, since it uses less digits than its factorization.

21211704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12844 (or 12837 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21211704 is about 4605.6165711010. The cubic root of 21211704 is about 276.8164231738.

Adding to 21211704 its reverse (40711212), we get a palindrome (61922916).

The spelling of 21211704 in words is "twenty-one million, two hundred eleven thousand, seven hundred four".