21731206 has 12 divisors (see below), whose sum is σ = 37918908. Its totient is φ = 9313332.

The previous prime is 21731191. The next prime is 21731239. The reversal of 21731206 is 60213712.

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 5 ways as a sum of consecutive naturals, for example, 110776 + ... + 110971.

It is an arithmetic number, because the mean of its divisors is an integer number (3159909).

Almost surely, 2^21731206 is an apocalyptic number.

21731206 is a deficient number, since it is larger than the sum of its proper divisors (16187702).

21731206 is a wasteful number, since it uses less digits than its factorization.

21731206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221763 (or 221756 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21731206 is about 4661.6741627874. The cubic root of 21731206 is about 279.0580849676.

Adding to 21731206 its reverse (60213712), we get a palindrome (81944918).

The spelling of 21731206 in words is "twenty-one million, seven hundred thirty-one thousand, two hundred six".