21231206 has 4 divisors (see below), whose sum is σ = 31846812. Its totient is φ = 10615602.

The previous prime is 21231173. The next prime is 21231241. The reversal of 21231206 is 60213212.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5307800 + ... + 5307803.

It is an arithmetic number, because the mean of its divisors is an integer number (7961703).

Almost surely, 2^21231206 is an apocalyptic number.

21231206 is a deficient number, since it is larger than the sum of its proper divisors (10615606).

21231206 is a wasteful number, since it uses less digits than its factorization.

21231206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10615605.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 21231206 is about 4607.7332822115. The cubic root of 21231206 is about 276.9012320177.

Adding to 21231206 its reverse (60213212), we get a palindrome (81444418).

The spelling of 21231206 in words is "twenty-one million, two hundred thirty-one thousand, two hundred six".