21340666 has 4 divisors (see below), whose sum is σ = 32011002. Its totient is φ = 10670332.

The previous prime is 21340663. The next prime is 21340721. The reversal of 21340666 is 66604312.

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., 19105641 + 2235025 = 4371^2 + 1495^2 .

It is not an unprimeable number, because it can be changed into a prime (21340663) by changing a digit.

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 as a sum of consecutive naturals, namely, 5335165 + ... + 5335168.

Almost surely, 2^21340666 is an apocalyptic number.

21340666 is a deficient number, since it is larger than the sum of its proper divisors (10670336).

21340666 is a wasteful number, since it uses less digits than its factorization.

21340666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10670335.

The product of its (nonzero) digits is 5184, while the sum is 28.

The square root of 21340666 is about 4619.5958697704. The cubic root of 21340666 is about 277.3762822697.

Adding to 21340666 its reverse (66604312), we get a palindrome (87944978).

The spelling of 21340666 in words is "twenty-one million, three hundred forty thousand, six hundred sixty-six".