21845566 has 4 divisors (see below), whose sum is σ = 32768352. Its totient is φ = 10922782.

The previous prime is 21845563. The next prime is 21845597. The reversal of 21845566 is 66554812.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21845563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5461390 + ... + 5461393.

It is an arithmetic number, because the mean of its divisors is an integer number (8192088).

Almost surely, 2^21845566 is an apocalyptic number.

21845566 is a deficient number, since it is larger than the sum of its proper divisors (10922786).

21845566 is a wasteful number, since it uses less digits than its factorization.

21845566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10922785.

The product of its digits is 57600, while the sum is 37.

The square root of 21845566 is about 4673.9240473076. The cubic root of 21845566 is about 279.5467411586.

It can be divided in two parts, 2184 and 5566, that added together give a triangular number (7750 = T₁₂₄).

The spelling of 21845566 in words is "twenty-one million, eight hundred forty-five thousand, five hundred sixty-six".