21650666 has 4 divisors (see below), whose sum is σ = 32476002. Its totient is φ = 10825332.

The previous prime is 21650653. The next prime is 21650683. The reversal of 21650666 is 66605612.

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 + 297025 = 4621^2 + 545^2 .

It is a Curzon number.

It is an unprimeable number.

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, 5412665 + ... + 5412668.

Almost surely, 2^21650666 is an apocalyptic number.

21650666 is a deficient number, since it is larger than the sum of its proper divisors (10825336).

21650666 is a wasteful number, since it uses less digits than its factorization.

21650666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10825335.

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

The square root of 21650666 is about 4653.0276165095. The cubic root of 21650666 is about 278.7129106678.

The spelling of 21650666 in words is "twenty-one million, six hundred fifty thousand, six hundred sixty-six".