21436661 has 4 divisors (see below), whose sum is σ = 21935232. Its totient is φ = 20938092.

The previous prime is 21436651. The next prime is 21436691. The reversal of 21436661 is 16663412.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21436661 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21436601) 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, 249221 + ... + 249306.

It is an arithmetic number, because the mean of its divisors is an integer number (5483808).

Almost surely, 2^21436661 is an apocalyptic number.

It is an amenable number.

21436661 is a deficient number, since it is larger than the sum of its proper divisors (498571).

21436661 is an equidigital number, since it uses as much as digits as its factorization.

21436661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 498570.

The product of its digits is 5184, while the sum is 29.

The square root of 21436661 is about 4629.9741899929. The cubic root of 21436661 is about 277.7915600214.

The spelling of 21436661 in words is "twenty-one million, four hundred thirty-six thousand, six hundred sixty-one".