21365573 has 2 divisors, whose sum is σ = 21365574. Its totient is φ = 21365572.

The previous prime is 21365569. The next prime is 21365579. The reversal of 21365573 is 37556312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13082689 + 8282884 = 3617^2 + 2878^2 .

It is a cyclic number.

It is not a de Polignac number, because 21365573 - 2² = 21365569 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21365579) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10682786 + 10682787.

It is an arithmetic number, because the mean of its divisors is an integer number (10682787).

Almost surely, 2^21365573 is an apocalyptic number.

It is an amenable number.

21365573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21365573 is an equidigital number, since it uses as much as digits as its factorization.

21365573 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18900, while the sum is 32.

The square root of 21365573 is about 4622.2908822358. The cubic root of 21365573 is about 277.4841502729.

The spelling of 21365573 in words is "twenty-one million, three hundred sixty-five thousand, five hundred seventy-three".