21739321 has 2 divisors, whose sum is σ = 21739322. Its totient is φ = 21739320.

The previous prime is 21739309. The next prime is 21739351. The reversal of 21739321 is 12393712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21724921 + 14400 = 4661^2 + 120^2 .

It is a cyclic number.

It is not a de Polignac number, because 21739321 - 2⁹ = 21738809 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21739321.

It is not a weakly prime, because it can be changed into another prime (21739351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10869660 + 10869661.

It is an arithmetic number, because the mean of its divisors is an integer number (10869661).

Almost surely, 2^21739321 is an apocalyptic number.

It is an amenable number.

21739321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21739321 is an equidigital number, since it uses as much as digits as its factorization.

21739321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2268, while the sum is 28.

The square root of 21739321 is about 4662.5444769997. The cubic root of 21739321 is about 279.0928165043.

The spelling of 21739321 in words is "twenty-one million, seven hundred thirty-nine thousand, three hundred twenty-one".