21423661 has 8 divisors (see below), whose sum is σ = 24525504. Its totient is φ = 18332160.

The previous prime is 21423641. The next prime is 21423673. The reversal of 21423661 is 16632412.

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

It is not a de Polignac number, because 21423661 - 2⁷ = 21423533 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 (21423601) 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 7 ways as a sum of consecutive naturals, for example, 2541 + ... + 7021.

It is an arithmetic number, because the mean of its divisors is an integer number (3065688).

Almost surely, 2^21423661 is an apocalyptic number.

It is an amenable number.

21423661 is a deficient number, since it is larger than the sum of its proper divisors (3101843).

21423661 is an equidigital number, since it uses as much as digits as its factorization.

21423661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5171.

The product of its digits is 1728, while the sum is 25.

The square root of 21423661 is about 4628.5700815695. The cubic root of 21423661 is about 277.7353942386.

The spelling of 21423661 in words is "twenty-one million, four hundred twenty-three thousand, six hundred sixty-one".