21887666 has 4 divisors (see below), whose sum is σ = 32831502. Its totient is φ = 10943832.

The previous prime is 21887647. The next prime is 21887669. The reversal of 21887666 is 66678812.

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., 21855625 + 32041 = 4675^2 + 179^2 .

It is not an unprimeable number, because it can be changed into a prime (21887669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5471915 + ... + 5471918.

Almost surely, 2^21887666 is an apocalyptic number.

21887666 is a deficient number, since it is larger than the sum of its proper divisors (10943836).

21887666 is a wasteful number, since it uses less digits than its factorization.

21887666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10943835.

The product of its digits is 193536, while the sum is 44.

The square root of 21887666 is about 4678.4255898753. The cubic root of 21887666 is about 279.7262034452.

The spelling of 21887666 in words is "twenty-one million, eight hundred eighty-seven thousand, six hundred sixty-six".