21410561 has 4 divisors (see below), whose sum is σ = 21547092. Its totient is φ = 21274032.

The previous prime is 21410537. The next prime is 21410563. The reversal of 21410561 is 16501412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12559936 + 8850625 = 3544^2 + 2975^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21410561 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21410563) 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, 68030 + ... + 68343.

It is an arithmetic number, because the mean of its divisors is an integer number (5386773).

Almost surely, 2^21410561 is an apocalyptic number.

It is an amenable number.

21410561 is a deficient number, since it is larger than the sum of its proper divisors (136531).

21410561 is a wasteful number, since it uses less digits than its factorization.

21410561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136530.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21410561 is about 4627.1547413070. The cubic root of 21410561 is about 277.6787734227.

Adding to 21410561 its reverse (16501412), we get a palindrome (37911973).

The spelling of 21410561 in words is "twenty-one million, four hundred ten thousand, five hundred sixty-one".