21884509 has 2 divisors, whose sum is σ = 21884510. Its totient is φ = 21884508.

The previous prime is 21884507. The next prime is 21884521. The reversal of 21884509 is 90548812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11580409 + 10304100 = 3403^2 + 3210^2 .

It is a cyclic number.

It is not a de Polignac number, because 21884509 - 2¹ = 21884507 is a prime.

Together with 21884507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21884503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10942254 + 10942255.

It is an arithmetic number, because the mean of its divisors is an integer number (10942255).

Almost surely, 2^21884509 is an apocalyptic number.

It is an amenable number.

21884509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21884509 is an equidigital number, since it uses as much as digits as its factorization.

21884509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23040, while the sum is 37.

The square root of 21884509 is about 4678.0881778778. The cubic root of 21884509 is about 279.7127538904.

The spelling of 21884509 in words is "twenty-one million, eight hundred eighty-four thousand, five hundred nine".