21566159 has 4 divisors (see below), whose sum is σ = 22701240. Its totient is φ = 20431080.

The previous prime is 21566147. The next prime is 21566189. The reversal of 21566159 is 95166512.

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

It is not a de Polignac number, because 21566159 - 2⁴ = 21566143 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21566119) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 567512 + ... + 567549.

It is an arithmetic number, because the mean of its divisors is an integer number (5675310).

Almost surely, 2^21566159 is an apocalyptic number.

21566159 is a deficient number, since it is larger than the sum of its proper divisors (1135081).

21566159 is a wasteful number, since it uses less digits than its factorization.

21566159 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1135080.

The product of its digits is 16200, while the sum is 35.

The square root of 21566159 is about 4643.9378764148. The cubic root of 21566159 is about 278.3498132481.

The spelling of 21566159 in words is "twenty-one million, five hundred sixty-six thousand, one hundred fifty-nine".