21920321 has 2 divisors, whose sum is σ = 21920322. Its totient is φ = 21920320.

The previous prime is 21920299. The next prime is 21920359. The reversal of 21920321 is 12302912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14737921 + 7182400 = 3839^2 + 2680^2 .

It is a cyclic number.

It is not a de Polignac number, because 21920321 - 2¹⁸ = 21658177 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21920293 and 21920302.

It is not a weakly prime, because it can be changed into another prime (21920621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10960160 + 10960161.

It is an arithmetic number, because the mean of its divisors is an integer number (10960161).

Almost surely, 2^21920321 is an apocalyptic number.

It is an amenable number.

21920321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21920321 is an equidigital number, since it uses as much as digits as its factorization.

21920321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21920321 is about 4681.9142452634. The cubic root of 21920321 is about 279.8652455318.

The spelling of 21920321 in words is "twenty-one million, nine hundred twenty thousand, three hundred twenty-one".