21660389 has 2 divisors, whose sum is σ = 21660390. Its totient is φ = 21660388.

The previous prime is 21660383. The next prime is 21660407. The reversal of 21660389 is 98306612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21548164 + 112225 = 4642^2 + 335^2 .

It is a cyclic number.

It is not a de Polignac number, because 21660389 - 2¹² = 21656293 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660383) 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 as a sum of consecutive naturals, namely, 10830194 + 10830195.

It is an arithmetic number, because the mean of its divisors is an integer number (10830195).

Almost surely, 2^21660389 is an apocalyptic number.

It is an amenable number.

21660389 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660389 is an equidigital number, since it uses as much as digits as its factorization.

21660389 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21660389 is about 4654.0723028333. The cubic root of 21660389 is about 278.7546263987.

The spelling of 21660389 in words is "twenty-one million, six hundred sixty thousand, three hundred eighty-nine".