21009346 has 4 divisors (see below), whose sum is σ = 31514022. Its totient is φ = 10504672.

The previous prime is 21009337. The next prime is 21009353. The reversal of 21009346 is 64390012.

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

It can be written as a sum of positive squares in only one way, i.e., 18792225 + 2217121 = 4335^2 + 1489^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21009346.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5252335 + ... + 5252338.

Almost surely, 2^21009346 is an apocalyptic number.

21009346 is a deficient number, since it is larger than the sum of its proper divisors (10504676).

21009346 is a wasteful number, since it uses less digits than its factorization.

21009346 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10504675.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 21009346 is about 4583.5953137248. The cubic root of 21009346 is about 275.9333399891.

Adding to 21009346 its reverse (64390012), we get a palindrome (85399358).

The spelling of 21009346 in words is "twenty-one million, nine thousand, three hundred forty-six".