21971566 has 8 divisors (see below), whose sum is σ = 33260040. Its totient is φ = 10884888.

The previous prime is 21971563. The next prime is 21971597. The reversal of 21971566 is 66517912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21971563) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 50176 + ... + 50611.

It is an arithmetic number, because the mean of its divisors is an integer number (4157505).

Almost surely, 2^21971566 is an apocalyptic number.

21971566 is a deficient number, since it is larger than the sum of its proper divisors (11288474).

21971566 is a wasteful number, since it uses less digits than its factorization.

21971566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100898.

The product of its digits is 22680, while the sum is 37.

The square root of 21971566 is about 4687.3837052241. The cubic root of 21971566 is about 280.0831640721.

The spelling of 21971566 in words is "twenty-one million, nine hundred seventy-one thousand, five hundred sixty-six".