21683666 has 4 divisors (see below), whose sum is σ = 32525502. Its totient is φ = 10841832.

The previous prime is 21683659. The next prime is 21683699. The reversal of 21683666 is 66638612.

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., 21669025 + 14641 = 4655^2 + 121^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5420915 + ... + 5420918.

Almost surely, 2^21683666 is an apocalyptic number.

21683666 is a deficient number, since it is larger than the sum of its proper divisors (10841836).

21683666 is a wasteful number, since it uses less digits than its factorization.

21683666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10841835.

The product of its digits is 62208, while the sum is 38.

The square root of 21683666 is about 4656.5723445470. The cubic root of 21683666 is about 278.8544437588.

The spelling of 21683666 in words is "twenty-one million, six hundred eighty-three thousand, six hundred sixty-six".