21784369 has 2 divisors, whose sum is σ = 21784370. Its totient is φ = 21784368.

The previous prime is 21784349. The next prime is 21784391. The reversal of 21784369 is 96348712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16096144 + 5688225 = 4012^2 + 2385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21784369 - 2¹⁵ = 21751601 is a prime.

It is a super-2 number, since 2×21784369² = 949117465456322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21784309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10892184 + 10892185.

It is an arithmetic number, because the mean of its divisors is an integer number (10892185).

Almost surely, 2^21784369 is an apocalyptic number.

It is an amenable number.

21784369 is a deficient number, since it is larger than the sum of its proper divisors (1).

21784369 is an equidigital number, since it uses as much as digits as its factorization.

21784369 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 21784369 is about 4667.3728156212. The cubic root of 21784369 is about 279.2854612658.

The spelling of 21784369 in words is "twenty-one million, seven hundred eighty-four thousand, three hundred sixty-nine".