21170561 has 8 divisors (see below), whose sum is σ = 21514080. Its totient is φ = 20829312.

The previous prime is 21170543. The next prime is 21170563. The reversal of 21170561 is 16507112.

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

It is a cyclic number.

It is not a de Polignac number, because 21170561 - 2¹⁰ = 21169537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21170563) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31121 + ... + 31793.

It is an arithmetic number, because the mean of its divisors is an integer number (2689260).

Almost surely, 2^21170561 is an apocalyptic number.

It is an amenable number.

21170561 is a deficient number, since it is larger than the sum of its proper divisors (343519).

21170561 is an equidigital number, since it uses as much as digits as its factorization.

21170561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1135.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21170561 is about 4601.1477915842. The cubic root of 21170561 is about 276.6373329007.

Adding to 21170561 its reverse (16507112), we get a palindrome (37677673).

The spelling of 21170561 in words is "twenty-one million, one hundred seventy thousand, five hundred sixty-one".