21560666 has 4 divisors (see below), whose sum is σ = 32341002. Its totient is φ = 10780332.

The previous prime is 21560647. The next prime is 21560689. The reversal of 21560666 is 66606512.

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., 21353641 + 207025 = 4621^2 + 455^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5390165 + ... + 5390168.

Almost surely, 2^21560666 is an apocalyptic number.

21560666 is a deficient number, since it is larger than the sum of its proper divisors (10780336).

21560666 is a wasteful number, since it uses less digits than its factorization.

21560666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10780335.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 21560666 is about 4643.3464225707. The cubic root of 21560666 is about 278.3261789150.

The spelling of 21560666 in words is "twenty-one million, five hundred sixty thousand, six hundred sixty-six".