21320641 has 4 divisors (see below), whose sum is σ = 22442800. Its totient is φ = 20198484.

The previous prime is 21320639. The next prime is 21320683. The reversal of 21320641 is 14602312.

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 not a de Polignac number, because 21320641 - 2¹ = 21320639 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19), and also a Moran number because the ratio is a prime number: 1122139 = 21320641 / (2 + 1 + 3 + 2 + 0 + 6 + 4 + 1).

It is not an unprimeable number, because it can be changed into a prime (21323641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 561051 + ... + 561088.

It is an arithmetic number, because the mean of its divisors is an integer number (5610700).

Almost surely, 2^21320641 is an apocalyptic number.

It is an amenable number.

21320641 is a deficient number, since it is larger than the sum of its proper divisors (1122159).

21320641 is a wasteful number, since it uses less digits than its factorization.

21320641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1122158.

The product of its (nonzero) digits is 288, while the sum is 19.

The square root of 21320641 is about 4617.4279637045. The cubic root of 21320641 is about 277.2894965011.

Adding to 21320641 its reverse (14602312), we get a palindrome (35922953).

The spelling of 21320641 in words is "twenty-one million, three hundred twenty thousand, six hundred forty-one".