21035666 has 4 divisors (see below), whose sum is σ = 31553502. Its totient is φ = 10517832.

The previous prime is 21035633. The next prime is 21035687. The reversal of 21035666 is 66653012.

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., 10699441 + 10336225 = 3271^2 + 3215^2 .

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 5258915 + ... + 5258918.

Almost surely, 2^21035666 is an apocalyptic number.

21035666 is a deficient number, since it is larger than the sum of its proper divisors (10517836).

21035666 is a wasteful number, since it uses less digits than its factorization.

21035666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10517835.

The product of its (nonzero) digits is 6480, while the sum is 29.

The square root of 21035666 is about 4586.4655236903. The cubic root of 21035666 is about 276.0485194403.

Adding to 21035666 its reverse (66653012), we get a palindrome (87688678).

The spelling of 21035666 in words is "twenty-one million, thirty-five thousand, six hundred sixty-six".