21362721 has 4 divisors (see below), whose sum is σ = 28483632. Its totient is φ = 14241812.

The previous prime is 21362717. The next prime is 21362729. The reversal of 21362721 is 12726312.

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 21362721 - 2² = 21362717 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21362691 and 21362700.

It is not an unprimeable number, because it can be changed into a prime (21362729) 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, 3560451 + ... + 3560456.

It is an arithmetic number, because the mean of its divisors is an integer number (7120908).

Almost surely, 2^21362721 is an apocalyptic number.

It is an amenable number.

21362721 is a deficient number, since it is larger than the sum of its proper divisors (7120911).

21362721 is an equidigital number, since it uses as much as digits as its factorization.

21362721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7120910.

The product of its digits is 1008, while the sum is 24.

The square root of 21362721 is about 4621.9823669071. The cubic root of 21362721 is about 277.4718029949.

The spelling of 21362721 in words is "twenty-one million, three hundred sixty-two thousand, seven hundred twenty-one".